On Wednesday 04 April 2007 00:01, Robert Watson wrote:
> On Sun, 1 Apr 2007, Robert Watson wrote:
> > The attached patch moves file descriptor locks from being a custom
> > mutex/sleep lock implemented using msleep() to an sx lock. With the new
> > sx lock optimizations in place, this is now sensible, avoiding both a
> > custom lock type and significantly improving performance. Kris has
> > reported 2x-4x improvement in transactions/sec with MySQL using this
> > patch, as it greatly reduces the cost of lock contention during file
> > descriptor lookup for threaded applications, and also moves to shared
> > locking to avoid exclusive acquisition for read-only operations (the vast
> > majority in most workloads). Patch is below, but you can also download
> > from:
> >
> > http://www.watson.org/~robert/freebsd/netperf/20070401a-filedesc-sx.diff
> >
> > I'm currently waiting for the sx lock changes to settle for a few days
> > before committing, so will plan to commit this around Wednesday/Thursday
> > of this week (unless serious problems arise).
>
> Andrzej has pointed out that shortly after I posted the patch, it came into
> conflict with changes in VFS. I've updated the patch and posted it at:
>
> http://www.watson.org/~robert/freebsd/netperf/20070403-filedesc-sx.diff
Just a small comment:
@@ -60,10 +60,7 @@
u_short fd_cmask; /* mask for file creation */
u_short fd_refcnt; /* thread reference count */
u_short fd_holdcnt; /* hold count on structure + mutex */
-
- struct mtx fd_mtx; /* protects members of this struct */
- int fd_locked; /* long lock flag */
- int fd_wanted; /* "" */
+ struct sx fd_sx; /* protects members of this struct */
struct kqlist fd_kqlist; /* list of kqueues on this filedesc */
int fd_holdleaderscount; /* block fdfree() for shared close() */
int fd_holdleaderswakeup; /* fdfree() needs wakeup */
Maybe it is better if you order the elements by size. Then you don't waste so
many extra bytes on platforms where the fields must be aligned.
struct {
struct sx fd_sx;
struct kqlist fd_kqlist;
int ...;
u_short ....;
};
--HPS
_______________________________________________
[email protected] mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-performance
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
