[lkml]   [2002]   [Aug]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] low-latency zap_page_range()
On Thu, Aug 29, 2002 at 10:37:02PM +0000, Linus Torvalds wrote:
> You will NOT.
> The page_table_lock protects against page stealing of the VM and
> concurrent page-faults, nothing else. There is no way you can get
> contention on it under any reasonable load that doesn't involve heavy
> out-of-memory behaviour, simply because
> - the lock is per-mm
> - all "regular" paths that care about this also get the mmap semaphore
> In short, that spinlock has _zero_ scalability impact. You can
> theoretically get contention on it without memory pressure only by
> having hundreds of threads page-faulting at the same time (getting a
> read-lock on the mmap semaphore), but by then your performance has
> nothing to do with the spinlock, and everything to do with the page
> faults themselves.
> (In fact, I can almost guarantee that most of the long hold-times are
> for exit(), not for munmap(). And in that case the spinlock cannot get
> any non-pagestealer contention at all, since nobody else is using the
> MM)

All I have to go on is a report this has happened and a low-priority
task to investigate it at some point in the future. I'll send you data
either demonstrating it or exonerating it when I eventually get to it.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:28    [W:0.048 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site