X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;ds=sidebyside;f=doc%2Fvm.texi;h=e6ff141067f58ce2b80cbb2f2a807a018267519d;hb=13753f29344700c01d9dc80834e51c7303ed18f7;hp=3703a94a5a301c147d55629007d69b6dfa746591;hpb=3fdd92584b84cb5f23249fc1121a67ad09a911e4;p=pintos-anon diff --git a/doc/vm.texi b/doc/vm.texi index 3703a94..e6ff141 100644 --- a/doc/vm.texi +++ b/doc/vm.texi @@ -420,11 +420,10 @@ Bits}) to implement an approximation to LRU. Your algorithm should perform at least as well as the ``second chance'' or ``clock'' algorithm. -Your design should allow for parallelism. Multiple processes should -be able to process page faults at once. If one page fault require +Your design should allow for parallelism. If one page fault requires I/O, in the meantime processes that do not fault should continue -executing and other page faults that do not require I/O should be able to -complete. These criteria require some synchronization effort. +executing and other page faults that do not require I/O should be able +to complete. These criteria require some synchronization effort. @node Lazy Loading @subsection Lazy Loading @@ -441,25 +440,25 @@ be written to swap. The core of the program loader is the loop in @func{load_segment} in @file{userprog/process.c}. -Each time around the loop, @code{read_bytes} receives the number of -bytes to read from the executable file and @code{zero_bytes} receives +Each time around the loop, @code{page_read_bytes} receives the number of +bytes to read from the executable file and @code{page_zero_bytes} receives the number of bytes to initialize to zero following the bytes read. The two always sum to @code{PGSIZE} (4,096). The handling of a page depends on these variables' values: @itemize @bullet @item -If @code{read_bytes} equals @code{PGSIZE}, the page should be demand +If @code{page_read_bytes} equals @code{PGSIZE}, the page should be demand paged from disk on its first access. @item -If @code{zero_bytes} equals @code{PGSIZE}, the page does not need to +If @code{page_zero_bytes} equals @code{PGSIZE}, the page does not need to be read from disk at all because it is all zeroes. You should handle such pages by creating a new page consisting of all zeroes at the first page fault. @item -If neither @code{read_bytes} nor @code{zero_bytes} equals +If neither @code{page_read_bytes} nor @code{page_zero_bytes} equals @code{PGSIZE}, then part of the page is to be read from disk and the remainder zeroed. This is a special case. You are allowed to handle it by reading the partial page from disk at executable load time and