Jeff Trawick wrote:
maybe increasing the granularity of the lock could help (multiple busy lists with the inode used as a hash to get to the proper busy list)
I happen to have a module, unrelated to mod_fcgid, which manages a fairly large shared-memory cache across a number of user sessions. Over the years I ended up with an implementation that divides it into 32 subcaches and gives each one a global lock; sessions are spread across the subcaches randomly. It may not be elegant but it works well under a pretty high load. Because this runs on Linux and we're just using the APR defaults, the process locks are SysV semaphores. Maybe sometime in the far future, once glibc 2.10 appears on our systems, we might try APR_LOCK_PROC_PTHREAD and see if we can't get the shiny new pthread_mutexattr_setrobust() support into APR. (As a side note, anyone know if this has come up yet in the APR world, maybe for a recent Fedora or something? I'm not sure what distros might have glibc 2.10 in them at all.) Anyhoo, the other thing I've pondered over the years but never tried would be to hack APR's SysV semaphore lock code to permit multiple semaphores in a set -- right now it's just a semget(..., 1, ...) but it would clean up our ipcs output a lot if we could pack those 32 semaphores into one set instead of having just one each in its own set, and especially so if we ever needed more than 32. Well, none of that is related to what I'm supposed to be doing this week (i.e., breaking out my old fcgid patches), nor httpd, really, but it's maybe mildly interesting to someone, or not, as the case may be. :-/ OK, back to work. Chris. -- GPG Key ID: 366A375B GPG Key Fingerprint: 485E 5041 17E1 E2BB C263 E4DE C8E3 FA36 366A 375B
