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authorEric Dumazet <dada1@cosmosbay.com>2006-03-23 06:00:12 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-23 10:38:09 -0500
commit0c9e63fd38a2fb2181668a0cdd622a3c23cfd567 (patch)
tree8fdb91603347b1da2e83a095ebcaab44b2c3c237 /kernel
parentd8733c2956968a01394a4d2a9e97a8b431a78776 (diff)
[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 'kernel')
-rw-r--r--kernel/fork.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 9bd7b65ee418..c79ae0b19a49 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -607,12 +607,12 @@ static struct files_struct *alloc_files(void)
607 atomic_set(&newf->count, 1); 607 atomic_set(&newf->count, 1);
608 608
609 spin_lock_init(&newf->file_lock); 609 spin_lock_init(&newf->file_lock);
610 newf->next_fd = 0;
610 fdt = &newf->fdtab; 611 fdt = &newf->fdtab;
611 fdt->next_fd = 0;
612 fdt->max_fds = NR_OPEN_DEFAULT; 612 fdt->max_fds = NR_OPEN_DEFAULT;
613 fdt->max_fdset = __FD_SETSIZE; 613 fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
614 fdt->close_on_exec = &newf->close_on_exec_init; 614 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
615 fdt->open_fds = &newf->open_fds_init; 615 fdt->open_fds = (fd_set *)&newf->open_fds_init;
616 fdt->fd = &newf->fd_array[0]; 616 fdt->fd = &newf->fd_array[0];
617 INIT_RCU_HEAD(&fdt->rcu); 617 INIT_RCU_HEAD(&fdt->rcu);
618 fdt->free_files = NULL; 618 fdt->free_files = NULL;