From 0c9e63fd38a2fb2181668a0cdd622a3c23cfd567 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 23 Mar 2006 03:00:12 -0800 Subject: [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/init_task.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'include/linux/init_task.h') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index dcfd2ecccb5..92146f3b742 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -7,11 +7,10 @@ #define INIT_FDTABLE \ { \ .max_fds = NR_OPEN_DEFAULT, \ - .max_fdset = __FD_SETSIZE, \ - .next_fd = 0, \ + .max_fdset = EMBEDDED_FD_SET_SIZE, \ .fd = &init_files.fd_array[0], \ - .close_on_exec = &init_files.close_on_exec_init, \ - .open_fds = &init_files.open_fds_init, \ + .close_on_exec = (fd_set *)&init_files.close_on_exec_init, \ + .open_fds = (fd_set *)&init_files.open_fds_init, \ .rcu = RCU_HEAD_INIT, \ .free_files = NULL, \ .next = NULL, \ @@ -20,9 +19,10 @@ #define INIT_FILES \ { \ .count = ATOMIC_INIT(1), \ - .file_lock = SPIN_LOCK_UNLOCKED, \ .fdt = &init_files.fdtab, \ .fdtab = INIT_FDTABLE, \ + .file_lock = SPIN_LOCK_UNLOCKED, \ + .next_fd = 0, \ .close_on_exec_init = { { 0, } }, \ .open_fds_init = { { 0, } }, \ .fd_array = { NULL, } \ -- cgit v1.2.3-70-g09d2 From c7c6464117a02b0d54feb4ebeca4db70fa493678 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:09 -0800 Subject: [PATCH] pidhash: don't use zero pids daemonize() calls set_special_pids(1,1), while init and kernel threads spawned from init/main.c:init() run with 0,0 special pids. This patch changes INIT_SIGNALS() so that that they run with ->pgrp == ->session == 1 also. This patch relies on fact that swapper's pid == 1. Now we have no hashed zero pids in pid_hash[]. User-space visibible change is that now /sbin/init runs with (1,1) special pids and becomes a session leader. Quoting Eric W. Biederman: > > daemonize consuming pids (1,1) then consumes pgrp 1. So that when > /sbin/init calls setsid() it thinks /sbin/init is a process group > leader and setsid() fails. So /sbin/init wants pgrp 1 session 1 > but doesn't get it. I am pretty certain daemonize did not exist so > /sbin/init got pgrp 1 session 1 in 2.4. > > That is the bug that is being fixed. > > This patch takes things one step farther and essentially calls > setsid() for pid == 1 before init is execed. That is new behavior > but it cleans up the kernel as we now do not need to support the > case of a process without a process group or a session. > > The only process that could have possibly cared was /sbin/init > and it already calls setsid() because it doesn't want that. > > If this was going to break anything noticeable the change in behavior > from 2.4 to 2.6 would have already done that. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/init_task.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/init_task.h') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 92146f3b742..41ecbb847f3 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -62,6 +62,8 @@ .posix_timers = LIST_HEAD_INIT(sig.posix_timers), \ .cpu_timers = INIT_CPU_TIMERS(sig.cpu_timers), \ .rlim = INIT_RLIMITS, \ + .pgrp = 1, \ + .session = 1, \ } #define INIT_SIGHAND(sighand) { \ -- cgit v1.2.3-70-g09d2