diff options
author | Steven Whitehouse <swhiteho@redhat.com> | 2007-01-17 16:33:23 +0100 |
---|---|---|
committer | Steven Whitehouse <swhiteho@redhat.com> | 2007-02-05 19:37:11 +0100 |
commit | fee852e374fb367c5436b1226eb93b35f8355ed9 (patch) | |
tree | 0e373afa25bd27582b2fc4fff8f2964ff0de6722 /fs/gfs2/glock.c | |
parent | [GFS2] Remove max_atomic_write tunable (diff) | |
download | linux-fee852e374fb367c5436b1226eb93b35f8355ed9.tar.xz linux-fee852e374fb367c5436b1226eb93b35f8355ed9.zip |
[GFS2] Shrink gfs2_inode memory by half
Here is something I spotted (while looking for something entirely
different) the other day.
Rather than using a completion in each and every struct gfs2_holder,
this removes it in favour of hashed wait queues, thus saving a
considerable amount of memory both on the stack (where a number of
gfs2_holder structures are allocated) and in particular in the
gfs2_inode which has 8 gfs2_holder structures embedded within it.
As a result on x86_64 the gfs2_inode shrinks from 2488 bytes to
1912 bytes, a saving of 576 bytes per inode (no thats not a typo!).
In actual practice we get a much better result than that since
now that a gfs2_inode is under the 2048 byte barrier, we get two
per 4k slab page effectively halving the amount of memory required
to store gfs2_inodes.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/gfs2/glock.c')
-rw-r--r-- | fs/gfs2/glock.c | 66 |
1 files changed, 43 insertions, 23 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index fb1960b7fdde..5341e03b873f 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -19,6 +19,7 @@ #include <linux/gfs2_ondisk.h> #include <linux/list.h> #include <linux/lm_interface.h> +#include <linux/wait.h> #include <asm/uaccess.h> #include "gfs2.h" @@ -395,7 +396,6 @@ void gfs2_holder_init(struct gfs2_glock *gl, unsigned int state, unsigned flags, gh->gh_flags = flags; gh->gh_error = 0; gh->gh_iflags = 0; - init_completion(&gh->gh_wait); if (gh->gh_state == LM_ST_EXCLUSIVE) gh->gh_flags |= GL_LOCAL_EXCL; @@ -479,6 +479,29 @@ static void gfs2_holder_put(struct gfs2_holder *gh) kfree(gh); } +static void gfs2_holder_dispose_or_wake(struct gfs2_holder *gh) +{ + if (test_bit(HIF_DEALLOC, &gh->gh_iflags)) { + gfs2_holder_put(gh); + return; + } + clear_bit(HIF_WAIT, &gh->gh_iflags); + smp_mb(); + wake_up_bit(&gh->gh_iflags, HIF_WAIT); +} + +static int holder_wait(void *word) +{ + schedule(); + return 0; +} + +static void wait_on_holder(struct gfs2_holder *gh) +{ + might_sleep(); + wait_on_bit(&gh->gh_iflags, HIF_WAIT, holder_wait, TASK_UNINTERRUPTIBLE); +} + /** * rq_mutex - process a mutex request in the queue * @gh: the glock holder @@ -493,7 +516,9 @@ static int rq_mutex(struct gfs2_holder *gh) list_del_init(&gh->gh_list); /* gh->gh_error never examined. */ set_bit(GLF_LOCK, &gl->gl_flags); - complete(&gh->gh_wait); + clear_bit(HIF_WAIT, &gh->gh_flags); + smp_mb(); + wake_up_bit(&gh->gh_iflags, HIF_WAIT); return 1; } @@ -549,7 +574,7 @@ static int rq_promote(struct gfs2_holder *gh) gh->gh_error = 0; set_bit(HIF_HOLDER, &gh->gh_iflags); - complete(&gh->gh_wait); + gfs2_holder_dispose_or_wake(gh); return 0; } @@ -573,10 +598,7 @@ static int rq_demote(struct gfs2_holder *gh) list_del_init(&gh->gh_list); gh->gh_error = 0; spin_unlock(&gl->gl_spin); - if (test_bit(HIF_DEALLOC, &gh->gh_iflags)) - gfs2_holder_put(gh); - else - complete(&gh->gh_wait); + gfs2_holder_dispose_or_wake(gh); spin_lock(&gl->gl_spin); } else { gl->gl_req_gh = gh; @@ -684,6 +706,8 @@ static void gfs2_glmutex_lock(struct gfs2_glock *gl) gfs2_holder_init(gl, 0, 0, &gh); set_bit(HIF_MUTEX, &gh.gh_iflags); + if (test_and_set_bit(HIF_WAIT, &gh.gh_iflags)) + BUG(); spin_lock(&gl->gl_spin); if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) { @@ -691,11 +715,13 @@ static void gfs2_glmutex_lock(struct gfs2_glock *gl) } else { gl->gl_owner = current; gl->gl_ip = (unsigned long)__builtin_return_address(0); - complete(&gh.gh_wait); + clear_bit(HIF_WAIT, &gh.gh_iflags); + smp_mb(); + wake_up_bit(&gh.gh_iflags, HIF_WAIT); } spin_unlock(&gl->gl_spin); - wait_for_completion(&gh.gh_wait); + wait_on_holder(&gh); gfs2_holder_uninit(&gh); } @@ -774,6 +800,7 @@ restart: return; set_bit(HIF_DEMOTE, &new_gh->gh_iflags); set_bit(HIF_DEALLOC, &new_gh->gh_iflags); + set_bit(HIF_WAIT, &new_gh->gh_iflags); goto restart; } @@ -908,12 +935,8 @@ static void xmote_bh(struct gfs2_glock *gl, unsigned int ret) gfs2_glock_put(gl); - if (gh) { - if (test_bit(HIF_DEALLOC, &gh->gh_iflags)) - gfs2_holder_put(gh); - else - complete(&gh->gh_wait); - } + if (gh) + gfs2_holder_dispose_or_wake(gh); } /** @@ -999,12 +1022,8 @@ static void drop_bh(struct gfs2_glock *gl, unsigned int ret) gfs2_glock_put(gl); - if (gh) { - if (test_bit(HIF_DEALLOC, &gh->gh_iflags)) - gfs2_holder_put(gh); - else - complete(&gh->gh_wait); - } + if (gh) + gfs2_holder_dispose_or_wake(gh); } /** @@ -1105,8 +1124,7 @@ static int glock_wait_internal(struct gfs2_holder *gh) if (gh->gh_flags & LM_FLAG_PRIORITY) do_cancels(gh); - wait_for_completion(&gh->gh_wait); - + wait_on_holder(gh); if (gh->gh_error) return gh->gh_error; @@ -1162,6 +1180,8 @@ static void add_to_queue(struct gfs2_holder *gh) struct gfs2_holder *existing; BUG_ON(!gh->gh_owner); + if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags)) + BUG(); existing = find_holder_by_owner(&gl->gl_holders, gh->gh_owner); if (existing) { |