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authorEric Dumazet <dada1@cosmosbay.com>2006-03-23 03:00:12 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-23 07:38:09 -0800
commit0c9e63fd38a2fb2181668a0cdd622a3c23cfd567 (patch)
tree8fdb91603347b1da2e83a095ebcaab44b2c3c237 /fs/open.c
parentd8733c2956968a01394a4d2a9e97a8b431a78776 (diff)
downloadlwn-0c9e63fd38a2fb2181668a0cdd622a3c23cfd567.tar.gz
lwn-0c9e63fd38a2fb2181668a0cdd622a3c23cfd567.zip
[PATCH] Shrinks sizeof(files_struct) and better layout
1) Reduce the size of (struct fdtable) to exactly 64 bytes on 32bits platforms, lowering kmalloc() allocated space by 50%. 2) Reduce the size of (files_struct), using a special 32 bits (or 64bits) embedded_fd_set, instead of a 1024 bits fd_set for the close_on_exec_init and open_fds_init fields. This save some ram (248 bytes per task) as most tasks dont open more than 32 files. D-Cache footprint for such tasks is also reduced to the minimum. 3) Reduce size of allocated fdset. Currently two full pages are allocated, that is 32768 bits on x86 for example, and way too much. The minimum is now L1_CACHE_BYTES. UP and SMP should benefit from this patch, because most tasks will touch only one cache line when open()/close() stdin/stdout/stderr (0/1/2), (next_fd, close_on_exec_init, open_fds_init, fd_array[0 .. 2] being in the same cache line) Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/open.c')
-rw-r--r--fs/open.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/open.c b/fs/open.c
index 70e0230d8e77..1091dadd6c38 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -973,7 +973,7 @@ repeat:
fdt = files_fdtable(files);
fd = find_next_zero_bit(fdt->open_fds->fds_bits,
fdt->max_fdset,
- fdt->next_fd);
+ files->next_fd);
/*
* N.B. For clone tasks sharing a files structure, this test
@@ -998,7 +998,7 @@ repeat:
FD_SET(fd, fdt->open_fds);
FD_CLR(fd, fdt->close_on_exec);
- fdt->next_fd = fd + 1;
+ files->next_fd = fd + 1;
#if 1
/* Sanity check */
if (fdt->fd[fd] != NULL) {
@@ -1019,8 +1019,8 @@ static void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
struct fdtable *fdt = files_fdtable(files);
__FD_CLR(fd, fdt->open_fds);
- if (fd < fdt->next_fd)
- fdt->next_fd = fd;
+ if (fd < files->next_fd)
+ files->next_fd = fd;
}
void fastcall put_unused_fd(unsigned int fd)