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| author | Frans Kaashoek <[email protected]> | 2019-08-01 16:52:38 -0400 |
|---|---|---|
| committer | Frans Kaashoek <[email protected]> | 2019-08-01 16:52:38 -0400 |
| commit | b02ef59e1498b3fa2eebeb12bf17548082695414 (patch) | |
| tree | 821cbb9ba189ceb5daee50b7e96fc8eb6fa09b72 | |
| parent | 62ece4b09e6a568ede0e3b524af959194e0cb792 (diff) | |
| download | xv6-labs-b02ef59e1498b3fa2eebeb12bf17548082695414.tar.gz xv6-labs-b02ef59e1498b3fa2eebeb12bf17548082695414.tar.bz2 xv6-labs-b02ef59e1498b3fa2eebeb12bf17548082695414.zip | |
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| -rw-r--r-- | labs/cow.html | 20 | ||||
| -rw-r--r-- | labs/lazy.html | 2 |
2 files changed, 16 insertions, 6 deletions
diff --git a/labs/cow.html b/labs/cow.html index c8a0c1d..2cc18fa 100644 --- a/labs/cow.html +++ b/labs/cow.html @@ -1,11 +1,18 @@ -<h2>Programming Assignment: Copy-on-Write Fork for xv6</h2> +<html> +<head> +<title>Lab: Copy-on-Write Fork for xv6</title> +<link rel="stylesheet" href="homework.css" type="text/css" /> +</head> +<body> + +<h1>Lab: Copy-on-Write Fork for xv6</h2> <p> Your task is implement copy-on-write fork in the xv6 kernel. You are done if your modified kernel executes both the cow and usertests programs successfully. -<h3>The problem</h3> +<h2>The problem</h2> The fork() system call in xv6 copies all of the parent process's user-space memory into the child. If the parent is large, copying can @@ -17,7 +24,7 @@ the copied pages are thrown away without ever being used. Of course, sometimes both child and parent modify memory at the same virtual address after a fork(), so for some pages the copying is truly needed. -<h3>The solution</h3> +<h2>The solution</h2> The goal of copy-on-write (COW) fork() is to defer allocating and copying physical memory pages for the child until they are actually @@ -41,7 +48,7 @@ memory a little trickier. A given physical page may be referred to by multiple processes' page tables, and should be freed when the last reference disappears. -<h3>The cow test program</h3> +<h2>The cow test program</h2> To help you test your implementation, we've provided an xv6 program called cow (source in user/cow.c). cow runs various tests, but @@ -80,7 +87,7 @@ ALL TESTS PASSED $ </pre> -<h3>Hints</h3> +<h2>Hints</h2> Here's one reasonable plan of attack. Modify uvmcopy() to map the parent's physical pages into the child, instead of allocating new @@ -97,3 +104,6 @@ same scheme as page faults when it encounters a COW page. It may be useful to have a way to record, for each PTE, whether it is a COW mapping. You can use the RSW (reserved for software) bits in the RISC-V PTE for this. + +</body> +</html> diff --git a/labs/lazy.html b/labs/lazy.html index baf5f3b..9d97cab 100644 --- a/labs/lazy.html +++ b/labs/lazy.html @@ -99,7 +99,7 @@ hi</tt> working. You should get at least one page fault (and thus lazy allocation) in the shell, and perhaps two. <p>If you have the basics working, now turn your implementation into - one that handles the corner cases too. + one that handles the corner cases too: <ul> |