site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com On Aug 10, 2006, at 12:02 PM, darwin-dev-request@lists.apple.com wrote: Just a quick question! I'm running an app which is used for testing i/o. Right now, I'm running a thread at an elevated priority which does a lot of pread() calls. The app works fine but is a little slow & right now, I'm fine-tuning it. One issue, though; when I fire up BigTop, find my process and look at the system call throughput, I notice that it appears to be capped at 9000 calls/sec. I'm guessing this is being throttled by a kernel parameter. Your guess (with regards to a limit on the syscall rate) is incorrect. I have observed a single-process syscall rate over 650,000/sec on an intel Mini, so your 9,000 is barely ticking over. The device I'm hitting is more than capable of beating that, so I'm definitely not saturating the driver. Thoughts / hints / ridicule welcome :-) This sentence is logically invalid. The *device* may well be capable of more than 9,000 IOTs/sec, but you haven't established anything at all regarding the driver here. Have you actually examined the interaction between driver and device to see what sort of utilisation you're seeing? Without more details of your test and driver architecture it's hard to offer you more suggestions. You are aware that the clustering layer and buffer cache will both affect the relationship between system calls and I/Os? Have you exercised your driver to see what it's maximal work rate is? Which system is your device in? How is it connected? Whose driver, and how is that driver architected? = Mike _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... This email sent to site_archiver@lists.apple.com