{"id":476842,"date":"2023-08-09T09:04:34","date_gmt":"2023-08-09T09:04:34","guid":{"rendered":""},"modified":"2023-09-05T11:13:34","modified_gmt":"2023-09-05T11:13:34","slug":"direct-memory-access","status":"publish","type":"wiki","link":"https:\/\/oneproxy.pro\/vn\/wiki\/direct-memory-access\/","title":{"rendered":"Truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp"},"content":{"rendered":"<h2>Gi\u1edbi thi\u1ec7u<\/h2>\n<p>Truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp (DMA) l\u00e0 m\u1ed9t c\u00f4ng ngh\u1ec7 quan tr\u1ecdng trong l\u0129nh v\u1ef1c h\u1ec7 th\u1ed1ng m\u00e1y t\u00ednh, cho ph\u00e9p truy\u1ec1n d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3 gi\u1eefa c\u00e1c thi\u1ebft b\u1ecb v\u00e0 b\u1ed9 nh\u1edb m\u00e0 kh\u00f4ng c\u1ea7n s\u1ef1 tham gia tr\u1ef1c ti\u1ebfp c\u1ee7a b\u1ed9 x\u1eed l\u00fd trung t\u00e2m (CPU). Kh\u1ea3 n\u0103ng n\u00e0y cho ph\u00e9p di chuy\u1ec3n d\u1eef li\u1ec7u nhanh h\u01a1n v\u00e0 h\u1ee3p l\u00fd h\u01a1n, khi\u1ebfn DMA tr\u1edf n\u00ean quan tr\u1ecdng trong c\u00e1c \u1ee9ng d\u1ee5ng kh\u00e1c nhau, bao g\u1ed3m k\u1ebft n\u1ed1i m\u1ea1ng, l\u01b0u tr\u1eef v\u00e0 x\u1eed l\u00fd \u0111a ph\u01b0\u01a1ng ti\u1ec7n.<\/p>\n<h2>Ngu\u1ed3n g\u1ed1c c\u1ee7a truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp<\/h2>\n<p>Kh\u00e1i ni\u1ec7m Truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp l\u1ea7n \u0111\u1ea7u ti\u00ean xu\u1ea5t hi\u1ec7n trong nh\u1eefng ng\u00e0y \u0111\u1ea7u c\u1ee7a \u0111i\u1ec7n to\u00e1n khi c\u00e1c k\u1ef9 s\u01b0 t\u00ecm c\u00e1ch gi\u1ea3m t\u1ea3i c\u00e1c t\u00e1c v\u1ee5 truy\u1ec1n d\u1eef li\u1ec7u t\u1eeb CPU sang ph\u1ea7n c\u1ee9ng chuy\u00ean d\u1ee5ng. Thu\u1eadt ng\u1eef \u201cDMA\u201d \u0111\u01b0\u1ee3c \u0111\u1eb7t ra v\u00e0o nh\u1eefng n\u0103m 1960, v\u1edbi nh\u1eefng tri\u1ec3n khai ban \u0111\u1ea7u xu\u1ea5t hi\u1ec7n trong c\u00e1c m\u00e1y t\u00ednh mini v\u00e0 h\u1ec7 th\u1ed1ng m\u00e1y t\u00ednh l\u1edbn. IBM \u0111\u01b0\u1ee3c ghi nh\u1eadn l\u00e0 ng\u01b0\u1eddi ti\u00ean phong trong DMA trong System\/360 Model 85, \u0111\u01b0\u1ee3c gi\u1edbi thi\u1ec7u v\u00e0o n\u0103m 1968.<\/p>\n<h2>Th\u00f4ng tin chi ti\u1ebft v\u1ec1 truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp<\/h2>\n<p>DMA cho ph\u00e9p c\u00e1c thi\u1ebft b\u1ecb, ch\u1eb3ng h\u1ea1n nh\u01b0 card m\u1ea1ng ho\u1eb7c b\u1ed9 \u0111i\u1ec1u khi\u1ec3n \u0111\u0129a, truy\u1ec1n d\u1eef li\u1ec7u tr\u1ef1c ti\u1ebfp \u0111\u1ebfn v\u00e0 t\u1eeb b\u1ed9 nh\u1edb c\u1ee7a h\u1ec7 th\u1ed1ng m\u00e0 kh\u00f4ng c\u1ea7n s\u1ef1 can thi\u1ec7p li\u00ean t\u1ee5c c\u1ee7a CPU. Thay v\u00ec I\/O truy\u1ec1n th\u1ed1ng do CPU \u0111i\u1ec1u khi\u1ec3n, trong \u0111\u00f3 CPU tham gia v\u00e0o t\u1eebng b\u01b0\u1edbc truy\u1ec1n d\u1eef li\u1ec7u, DMA cho ph\u00e9p d\u1eef li\u1ec7u truy\u1ec1n tr\u1ef1c ti\u1ebfp gi\u1eefa c\u00e1c thi\u1ebft b\u1ecb ngo\u1ea1i vi v\u00e0 b\u1ed9 nh\u1edb.<\/p>\n<h2>C\u1ea5u tr\u00fac b\u00ean trong c\u1ee7a truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp<\/h2>\n<p>Trung t\u00e2m c\u1ee7a DMA l\u00e0 b\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA (c\u00f2n \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 c\u00f4ng c\u1ee5 DMA ho\u1eb7c b\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA), qu\u1ea3n l\u00fd vi\u1ec7c truy\u1ec1n d\u1eef li\u1ec7u gi\u1eefa c\u00e1c thi\u1ebft b\u1ecb v\u00e0 b\u1ed9 nh\u1edb. B\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA c\u00f3 b\u1ed9 thanh ghi v\u00e0 logic ri\u00eang \u0111\u1ec3 x\u1eed l\u00fd chuy\u1ec3n \u0111\u1ed9ng d\u1eef li\u1ec7u. Khi m\u1ed9t thi\u1ebft b\u1ecb c\u1ea7n truy\u1ec1n d\u1eef li\u1ec7u, n\u00f3 s\u1ebd kh\u1edfi t\u1ea1o y\u00eau c\u1ea7u DMA t\u1edbi b\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA, ch\u1ec9 \u0111\u1ecbnh ngu\u1ed3n, \u0111\u00edch v\u00e0 l\u01b0\u1ee3ng d\u1eef li\u1ec7u c\u1ea7n truy\u1ec1n.<\/p>\n<p>C\u00e1c b\u01b0\u1edbc li\u00ean quan \u0111\u1ebfn chuy\u1ec3n DMA \u0111i\u1ec3n h\u00ecnh nh\u01b0 sau:<\/p>\n<ol>\n<li><strong>L\u1eddi y\u00eau c\u1ea7u<\/strong>: Thi\u1ebft b\u1ecb b\u1eaft \u0111\u1ea7u y\u00eau c\u1ea7u DMA, cho bi\u1ebft chi ti\u1ebft truy\u1ec1n d\u1eef li\u1ec7u.<\/li>\n<li><strong>Tr\u1ecdng t\u00e0i<\/strong>: N\u1ebfu nhi\u1ec1u thi\u1ebft b\u1ecb y\u00eau c\u1ea7u DMA \u0111\u1ed3ng th\u1eddi, b\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA s\u1ebd \u01b0u ti\u00ean c\u00e1c y\u00eau c\u1ea7u d\u1ef1a tr\u00ean s\u01a1 \u0111\u1ed3 ph\u00e2n x\u1eed \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh tr\u01b0\u1edbc.<\/li>\n<li><strong>Quy\u1ec1n s\u1edf h\u1eefu xe bu\u00fdt<\/strong>: B\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA gi\u00e0nh quy\u1ec1n ki\u1ec3m so\u00e1t t\u1ea1m th\u1eddi bus h\u1ec7 th\u1ed1ng t\u1eeb CPU.<\/li>\n<li><strong>Chuy\u1ec3n kho\u1ea3n<\/strong>: B\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA truy\u1ec1n d\u1eef li\u1ec7u tr\u1ef1c ti\u1ebfp gi\u1eefa thi\u1ebft b\u1ecb v\u00e0 b\u1ed9 nh\u1edb.<\/li>\n<li><strong>Ho\u00e0n th\u00e0nh<\/strong>: Sau khi qu\u00e1 tr\u00ecnh truy\u1ec1n ho\u00e0n t\u1ea5t, b\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA s\u1ebd th\u00f4ng b\u00e1o cho thi\u1ebft b\u1ecb v\u00e0 gi\u1ea3i ph\u00f3ng bus tr\u1edf l\u1ea1i CPU.<\/li>\n<\/ol>\n<h2>Ph\u00e2n t\u00edch c\u00e1c t\u00ednh n\u0103ng ch\u00ednh c\u1ee7a truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp<\/h2>\n<p>DMA cung c\u1ea5p m\u1ed9t s\u1ed1 t\u00ednh n\u0103ng ch\u00ednh khi\u1ebfn n\u00f3 tr\u1edf th\u00e0nh m\u1ed9t c\u00f4ng ngh\u1ec7 c\u00f3 gi\u00e1 tr\u1ecb:<\/p>\n<ol>\n<li><strong>Gi\u1ea3m chi ph\u00ed CPU<\/strong>: B\u1eb1ng c\u00e1ch gi\u1ea3m t\u1ea3i c\u00e1c t\u00e1c v\u1ee5 truy\u1ec1n d\u1eef li\u1ec7u kh\u1ecfi CPU, DMA gi\u1ea3i ph\u00f3ng c\u00e1c t\u00e0i nguy\u00ean x\u1eed l\u00fd c\u00f3 gi\u00e1 tr\u1ecb, cho ph\u00e9p CPU t\u1eadp trung v\u00e0o c\u00e1c t\u00e1c v\u1ee5 quan tr\u1ecdng h\u01a1n.<\/li>\n<li><strong>Truy\u1ec1n d\u1eef li\u1ec7u nhanh h\u01a1n<\/strong>: DMA truy\u1ec1n d\u1eef li\u1ec7u gi\u1eefa c\u00e1c thi\u1ebft b\u1ecb v\u00e0 b\u1ed9 nh\u1edb \u1edf t\u1ed1c \u0111\u1ed9 cao h\u01a1n c\u00e1c ph\u01b0\u01a1ng ph\u00e1p I\/O \u0111\u01b0\u1ee3c l\u1eadp tr\u00ecnh truy\u1ec1n th\u1ed1ng.<\/li>\n<li><strong>Ho\u1ea1t \u0111\u1ed9ng kh\u00f4ng \u0111\u1ed3ng b\u1ed9<\/strong>: DMA ho\u1ea1t \u0111\u1ed9ng \u0111\u1ed9c l\u1eadp v\u1edbi CPU, cho ph\u00e9p c\u00e1c thi\u1ebft b\u1ecb truy\u1ec1n d\u1eef li\u1ec7u \u0111\u1ed3ng th\u1eddi v\u1edbi ho\u1ea1t \u0111\u1ed9ng c\u1ee7a CPU.<\/li>\n<li><strong>Di chuy\u1ec3n d\u1eef li\u1ec7u h\u1ee3p l\u00fd<\/strong>: DMA lo\u1ea1i b\u1ecf nhu c\u1ea7u \u0111\u1ec7m trung gian, gi\u1ea3m \u0111\u1ed9 tr\u1ec5 v\u00e0 c\u1ea3i thi\u1ec7n hi\u1ec7u n\u0103ng h\u1ec7 th\u1ed1ng t\u1ed5ng th\u1ec3.<\/li>\n<\/ol>\n<h2>C\u00e1c lo\u1ea1i truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp<\/h2>\n<p>DMA c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c ph\u00e2n lo\u1ea1i th\u00e0nh ba lo\u1ea1i ch\u00ednh d\u1ef1a tr\u00ean h\u01b0\u1edbng truy\u1ec1n d\u1eef li\u1ec7u:<\/p>\n<table>\n<thead>\n<tr>\n<th>Ki\u1ec3u<\/th>\n<th>S\u1ef1 mi\u00eau t\u1ea3<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>DMA \u0111\u01a1n<\/strong><\/td>\n<td>Truy\u1ec1n d\u1eef li\u1ec7u x\u1ea3y ra gi\u1eefa m\u1ed9t thi\u1ebft b\u1ecb v\u00e0 b\u1ed9 nh\u1edb c\u1ee5 th\u1ec3.<\/td>\n<\/tr>\n<tr>\n<td><strong>DMA x\u1ebfp t\u1ea7ng<\/strong><\/td>\n<td>Nhi\u1ec1u b\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA \u0111\u01b0\u1ee3c n\u1ed1i chu\u1ed7i, cho ph\u00e9p n\u1ed1i chu\u1ed7i truy\u1ec1n d\u1eef li\u1ec7u gi\u1eefa c\u00e1c thi\u1ebft b\u1ecb.<\/td>\n<\/tr>\n<tr>\n<td><strong>Nhi\u1ec1u DMA<\/strong><\/td>\n<td>Chuy\u1ec3n DMA \u0111\u1ed3ng th\u1eddi gi\u1eefa nhi\u1ec1u thi\u1ebft b\u1ecb v\u00e0 b\u1ed9 nh\u1edb.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>C\u00e1ch s\u1eed d\u1ee5ng quy\u1ec1n truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp, v\u1ea5n \u0111\u1ec1 v\u00e0 gi\u1ea3i ph\u00e1p<\/h2>\n<h3>\u1ee8ng d\u1ee5ng c\u1ee7a DMA:<\/h3>\n<ul>\n<li><strong>M\u1ea1ng<\/strong>: DMA r\u1ea5t c\u1ea7n thi\u1ebft \u0111\u1ec3 truy\u1ec1n d\u1eef li\u1ec7u t\u1ed1c \u0111\u1ed9 cao trong th\u1ebb giao di\u1ec7n m\u1ea1ng (NIC), cho ph\u00e9p nh\u1eadn v\u00e0 truy\u1ec1n d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3.<\/li>\n<li><strong>Kho<\/strong>: DMA \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong b\u1ed9 \u0111i\u1ec1u khi\u1ec3n \u0111\u0129a \u0111\u1ec3 \u0111\u1ecdc v\u00e0 ghi d\u1eef li\u1ec7u t\u1eeb c\u00e1c thi\u1ebft b\u1ecb l\u01b0u tr\u1eef m\u00e0 kh\u00f4ng c\u1ea7n s\u1ef1 can thi\u1ec7p c\u1ee7a CPU.<\/li>\n<li><strong>X\u1eed l\u00fd \u00e2m thanh\/video<\/strong>: DMA t\u1ea1o \u0111i\u1ec1u ki\u1ec7n truy\u1ec1n d\u1eef li\u1ec7u theo th\u1eddi gian th\u1ef1c cho c\u00e1c \u1ee9ng d\u1ee5ng \u0111a ph\u01b0\u01a1ng ti\u1ec7n, gi\u1ea3m thi\u1ec3u \u0111\u1ed9 tr\u1ec5 \u00e2m thanh v\u00e0 video.<\/li>\n<\/ul>\n<h3>Nh\u1eefng th\u00e1ch th\u1ee9c v\u00e0 gi\u1ea3i ph\u00e1p:<\/h3>\n<ul>\n<li><strong>S\u1ef1 k\u1ebft h\u1ee3p d\u1eef li\u1ec7u<\/strong>: Vi\u1ec7c \u0111\u1ea3m b\u1ea3o t\u00ednh nh\u1ea5t qu\u00e1n c\u1ee7a d\u1eef li\u1ec7u gi\u1eefa CPU v\u00e0 thi\u1ebft b\u1ecb trong qu\u00e1 tr\u00ecnh truy\u1ec1n DMA c\u00f3 th\u1ec3 l\u00e0 m\u1ed9t th\u00e1ch th\u1ee9c. K\u1ef9 thu\u1eadt qu\u1ea3n l\u00fd b\u1ed9 \u0111\u1ec7m v\u00e0 c\u01a1 ch\u1ebf \u0111\u1ed3ng b\u1ed9 h\u00f3a th\u00edch h\u1ee3p \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 gi\u1ea3i quy\u1ebft v\u1ea5n \u0111\u1ec1 n\u00e0y.<\/li>\n<li><strong>Xung \u0111\u1ed9t DMA<\/strong>: Xung \u0111\u1ed9t c\u00f3 th\u1ec3 ph\u00e1t sinh khi nhi\u1ec1u thi\u1ebft b\u1ecb tranh gi\u00e0nh quy\u1ec1n truy c\u1eadp DMA c\u00f9ng m\u1ed9t l\u00fac. C\u01a1 ch\u1ebf ph\u00e2n x\u1eed v\u00e0 \u01b0u ti\u00ean ph\u00f9 h\u1ee3p l\u00e0 c\u1ea7n thi\u1ebft \u0111\u1ec3 tr\u00e1nh tranh ch\u1ea5p.<\/li>\n<li><strong>M\u1ed1i quan t\u00e2m v\u1ec1 b\u1ea3o m\u1eadt<\/strong>: Truy c\u1eadp tr\u00e1i ph\u00e9p v\u00e0o DMA c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn vi ph\u1ea1m an ninh. C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf h\u1ec7 th\u1ed1ng ph\u1ea3i tri\u1ec3n khai c\u00e1c c\u01a1 ch\u1ebf ki\u1ec3m so\u00e1t truy c\u1eadp m\u1ea1nh m\u1ebd \u0111\u1ec3 gi\u1ea3m thi\u1ec3u nh\u1eefng r\u1ee7i ro \u0111\u00f3.<\/li>\n<\/ul>\n<h2>\u0110\u1eb7c \u0111i\u1ec3m ch\u00ednh v\u00e0 so s\u00e1nh<\/h2>\n<table>\n<thead>\n<tr>\n<th>\u0111\u1eb7c tr\u01b0ng<\/th>\n<th>DMA<\/th>\n<th>V\u00e0o\/ra \u0111\u01b0\u1ee3c l\u1eadp tr\u00ecnh<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>S\u1ef1 tham gia c\u1ee7a CPU<\/strong><\/td>\n<td>Chuy\u1ec3n giao t\u1ed1i thi\u1ec3u, \u0111\u1ed9c l\u1eadp<\/td>\n<td>I\/O t\u1eebng b\u01b0\u1edbc, s\u1eed d\u1ee5ng nhi\u1ec1u CPU<\/td>\n<\/tr>\n<tr>\n<td><strong>T\u1ed1c \u0111\u1ed9<\/strong><\/td>\n<td>Truy\u1ec1n d\u1eef li\u1ec7u nhanh h\u01a1n<\/td>\n<td>Truy\u1ec1n d\u1eef li\u1ec7u ch\u1eadm h\u01a1n<\/td>\n<\/tr>\n<tr>\n<td><strong>Tr\u00ean kh\u00f4ng<\/strong><\/td>\n<td>Th\u1ea5p<\/td>\n<td>Cao<\/td>\n<\/tr>\n<tr>\n<td><strong>H\u01b0\u1edbng d\u1eef li\u1ec7u<\/strong><\/td>\n<td>hai chi\u1ec1u<\/td>\n<td>M\u1ed9t chi\u1ec1u<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Quan \u0111i\u1ec3m v\u00e0 c\u00f4ng ngh\u1ec7 t\u01b0\u01a1ng lai<\/h2>\n<p>T\u01b0\u01a1ng lai c\u1ee7a DMA \u0111\u1ea7y h\u1ee9a h\u1eb9n khi c\u00f4ng ngh\u1ec7 \u0111i\u1ec7n to\u00e1n ti\u1ebfp t\u1ee5c ph\u00e1t tri\u1ec3n. M\u1ed9t s\u1ed1 ph\u00e1t tri\u1ec3n ti\u1ec1m n\u0103ng bao g\u1ed3m:<\/p>\n<ul>\n<li><strong>Hi\u1ec7u su\u1ea5t n\u00e2ng cao<\/strong>: Nh\u1eefng ti\u1ebfn b\u1ed9 trong b\u1ed9 \u0111i\u1ec1u khi\u1ec3n DMA v\u00e0 ki\u1ebfn tr\u00fac bus s\u1ebd d\u1eabn \u0111\u1ebfn t\u1ed1c \u0111\u1ed9 truy\u1ec1n d\u1eef li\u1ec7u nhanh h\u01a1n, gi\u1ea3m \u0111\u1ed9 tr\u1ec5 v\u00e0 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t t\u1ed5ng th\u1ec3 c\u1ee7a h\u1ec7 th\u1ed1ng.<\/li>\n<li><strong>Hi\u1ec7u su\u1ea5t n\u0103ng l\u01b0\u1ee3ng<\/strong>: DMA c\u00f3 th\u1ec3 \u0111\u00f3ng g\u00f3p v\u00e0o h\u1ec7 th\u1ed1ng ti\u1ebft ki\u1ec7m n\u0103ng l\u01b0\u1ee3ng b\u1eb1ng c\u00e1ch gi\u1ea3m m\u1ee9c s\u1eed d\u1ee5ng CPU v\u00e0 m\u1ee9c ti\u00eau th\u1ee5 \u0111i\u1ec7n n\u0103ng li\u00ean quan.<\/li>\n<li><strong>T\u00edch h\u1ee3p v\u1edbi c\u00e1c c\u00f4ng ngh\u1ec7 m\u1edbi n\u1ed5i<\/strong>: DMA c\u00f3 th\u1ec3 s\u1ebd \u0111\u00f3ng m\u1ed9t vai tr\u00f2 quan tr\u1ecdng trong c\u00e1c c\u00f4ng ngh\u1ec7 m\u1edbi n\u1ed5i nh\u01b0 Internet of Things (IoT) v\u00e0 \u0111i\u1ec7n to\u00e1n bi\u00ean, cho ph\u00e9p trao \u0111\u1ed5i d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3 gi\u1eefa c\u00e1c thi\u1ebft b\u1ecb.<\/li>\n<\/ul>\n<h2>M\u00e1y ch\u1ee7 proxy v\u00e0 truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp<\/h2>\n<p>C\u00e1c m\u00e1y ch\u1ee7 proxy, nh\u01b0 OneProxy, c\u00f3 th\u1ec3 h\u01b0\u1edfng l\u1ee3i t\u1eeb DMA khi x\u1eed l\u00fd kh\u1ed1i l\u01b0\u1ee3ng l\u01b0u l\u01b0\u1ee3ng d\u1eef li\u1ec7u l\u1edbn. B\u1eb1ng c\u00e1ch truy\u1ec1n d\u1eef li\u1ec7u gi\u1eefa c\u00e1c m\u00e1y kh\u00e1ch v\u00e0 internet m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3, c\u00e1c m\u00e1y ch\u1ee7 proxy h\u1ed7 tr\u1ee3 DMA c\u00f3 th\u1ec3 c\u1ea3i thi\u1ec7n \u0111\u00e1ng k\u1ec3 th\u1eddi gian ph\u1ea3n h\u1ed3i v\u00e0 hi\u1ec7u su\u1ea5t t\u1ed5ng th\u1ec3. DMA c\u00f3 th\u1ec3 \u0111\u1eb7c bi\u1ec7t thu\u1eadn l\u1ee3i cho c\u00e1c m\u00e1y ch\u1ee7 proxy trong c\u00e1c t\u00ecnh hu\u1ed1ng c\u00f3 t\u1ea3i m\u1ea1ng cao ho\u1eb7c khi cung c\u1ea5p n\u1ed9i dung \u0111a ph\u01b0\u01a1ng ti\u1ec7n.<\/p>\n<h2>Li\u00ean k\u1ebft li\u00ean quan<\/h2>\n<p>\u0110\u1ec3 bi\u1ebft th\u00eam th\u00f4ng tin v\u1ec1 Truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp, b\u1ea1n c\u00f3 th\u1ec3 kh\u00e1m ph\u00e1 c\u00e1c t\u00e0i nguy\u00ean sau:<\/p>\n<ul>\n<li><a href=\"https:\/\/en.wikipedia.org\/wiki\/Direct_memory_access\" target=\"_new\" rel=\"noopener nofollow\">Wikipedia - Truy c\u1eadp b\u1ed9 nh\u1edb tr\u1ef1c ti\u1ebfp<\/a><\/li>\n<li><a href=\"https:\/\/www.techopedia.com\/definition\/27674\/direct-memory-access-dma\" target=\"_new\" rel=\"noopener nofollow\">Techopedia \u2013 DMA<\/a><\/li>\n<li><a href=\"https:\/\/www.redbooks.ibm.com\/abstracts\/sg244940.html\" target=\"_new\" rel=\"noopener nofollow\">S\u00e1ch \u0111\u1ecf IBM \u2013 Kh\u00e1i ni\u1ec7m v\u00e0 l\u1eadp tr\u00ecnh DMA<\/a><\/li>\n<\/ul>","protected":false},"featured_media":476843,"menu_order":0,"template":"","meta":{"_acf_changed":false,"content-type":"","inline_featured_image":false,"footnotes":""},"class_list":["post-476842","wiki","type-wiki","status-publish","has-post-thumbnail","hentry"],"acf":{"faq_title":"Frequently Asked Questions about <mark>Direct Memory Access (DMA)<\/mark>","faq_items":[{"question":"What is Direct Memory Access (DMA)?","answer":"<p><strong>Direct Memory Access (DMA)<\/strong> is a technology that allows devices to transfer data directly to and from the system's memory without involving the central processing unit (CPU). It enables faster data movement and reduces CPU overhead.<\/p>"},{"question":"How did Direct Memory Access originate?","answer":"<p>DMA's concept was introduced in the early days of computing during the 1960s. IBM's System\/360 Model 85, launched in 1968, is credited with pioneering DMA.<\/p>"},{"question":"How does Direct Memory Access work?","answer":"<p>DMA uses a dedicated DMA controller to manage data transfers between devices and memory. When a device needs to transfer data, it initiates a DMA request to the controller, which handles the data movement independently from the CPU.<\/p>"},{"question":"What are the key features of Direct Memory Access?","answer":"<p>DMA offers several key features, including reduced CPU overhead, faster data transfer, asynchronous operation, and streamlined data movement.<\/p>"},{"question":"What types of Direct Memory Access exist?","answer":"<p>DMA can be categorized into three main types based on data transfer direction: Single DMA (one device to memory), Cascade DMA (multiple controllers daisy-chained), and Multiple DMA (simultaneous transfers between multiple devices and memory).<\/p>"},{"question":"What are some applications of Direct Memory Access?","answer":"<p>DMA is used in networking for high-speed data transfers, storage for efficient disk I\/O, and multimedia processing for real-time audio and video streaming.<\/p>"},{"question":"What challenges are associated with Direct Memory Access?","answer":"<p>DMA may face challenges like data coherency, DMA conflicts, and security concerns. These issues are addressed through cache management, arbitration mechanisms, and robust access control.<\/p>"},{"question":"How does Direct Memory Access compare to Programmed I\/O?","answer":"<p>DMA involves minimal CPU involvement and offers faster data transfer, while Programmed I\/O is CPU-intensive and slower. DMA's overhead is low, whereas Programmed I\/O has higher overhead.<\/p>"},{"question":"What is the future of Direct Memory Access?","answer":"<p>The future of DMA looks promising with enhanced performance, improved energy efficiency, and integration with emerging technologies like IoT and edge computing.<\/p>"},{"question":"How are proxy servers related to Direct Memory Access?","answer":"<p>Proxy servers, such as OneProxy, can benefit from DMA by efficiently handling data traffic and improving overall performance in high-load scenarios or when serving multimedia content.<\/p>"}]},"_links":{"self":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki\/476842","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki"}],"about":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/types\/wiki"}],"version-history":[{"count":0,"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki\/476842\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/media\/476843"}],"wp:attachment":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/media?parent=476842"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}