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authorPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>2005-09-03 18:57:25 -0400
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 03:06:21 -0400
commit1e40cd383ccc7c9f8b338c56ce28c326e25eb2fe (patch)
tree8dab0fb849ccc25febf6c8f8865094141a50b8d2 /fs
parented1b58d8b53519e10a35c6a2bb49cac35f439621 (diff)
[PATCH] uml: fixes performance regression in activate_mm and thus exec()
Normally, activate_mm() is called from exec(), and thus it used to be a no-op because we use a completely new "MM context" on the host (for instance, a new process), and so we didn't need to flush any "TLB entries" (which for us are the set of memory mappings for the host process from the virtual "RAM" file). Kernel threads, instead, are usually handled in a different way. So, when for AIO we call use_mm(), things used to break and so Benjamin implemented activate_mm(). However, that is only needed for AIO, and could slow down exec() inside UML, so be smart: detect being called for AIO (via PF_BORROWED_MM) and do the full flush only in that situation. Comment also the caller so that people won't go breaking UML without noticing. I also rely on the caller's locks for testing current->flags. Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> CC: Benjamin LaHaise <bcrl@kvack.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/aio.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 06d7d4390fe7..4f641abac3c0 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -567,6 +567,10 @@ static void use_mm(struct mm_struct *mm)
567 atomic_inc(&mm->mm_count); 567 atomic_inc(&mm->mm_count);
568 tsk->mm = mm; 568 tsk->mm = mm;
569 tsk->active_mm = mm; 569 tsk->active_mm = mm;
570 /*
571 * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
572 * it won't work. Update it accordingly if you change it here
573 */
570 activate_mm(active_mm, mm); 574 activate_mm(active_mm, mm);
571 task_unlock(tsk); 575 task_unlock(tsk);
572 576