-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 08/13/2014 07:11 AM, Peter Zijlstra wrote: > On Wed, Aug 13, 2014 at 08:59:50AM +0200, Mike Galbraith wrote: > >> I was told that clock_gettime(CLOCK_PROCESS_CPUTIME_ID) has >> scalability issues on BIG boxen > >> I'm sure the real clock_gettime() using proggy that gummed up a >> ~1200 core box for "a while" wasn't the testcase below, which >> will gum it up for a long while, but looks to me like using >> CLOCK_PROCESS_CPUTIME_ID from LOTS of threads is a "Don't do >> that, it'll hurt a LOT". > > Yes, don't do that. Its unavoidably slow and bad.
I don't see why that needs the tasklist_lock, when do_sys_times grabs a different lock. If the same bottleneck exists from multiple places, maybe it does make sense to have a seqlock for the statistics at the sighand level? I can code up a patch that does that, and throw it over the wall to people with big systems who hit that bottleneck on a regular basis... - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJT62b2AAoJEM553pKExN6DBJ4H/AyVsN4N73Gp/wrm7waaNjpS kU5R2pIGzJqxJ4BZi+aeiuT09ZoSHCl3nvSsMNBm712NX1jyFVC4I91ON18tsB3o P/tipcCP9Q6QSW8+lPRNz459OsaXX+wyRxcdnUtZN7SVb+NTWlxZ4o8UiVljZYSV 2mRr2ipd/0vKn7J9twaIP0UMddTpIrnMTCMKookoWXoHeJIXsYAs3XTRsoPJAddz 0ba5H7OGjphOSCyMkDDo3GG+K8oHJIpD8PHT38pXfX+suNEGxMO7PGvvEyUcrJKx 5355fnU6/1mksPlRD5DIwMowMjbY5zy71P8Lv4Eg+LY+C/kGjyrz9Maa0SyRMh8= =VQ/m -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
