Date: Wed, 27 Jun 2018 08:11:13 -0600 From: Warner Losh <imp@bsdimp.com> To: Steevan Rodrigues <steevanxperia@gmail.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: high CPU usage in FreeBSD for a PCIe card driver Message-ID: <CANCZdfoO6HsxiCt_SC8n1Jb3GhmbMewAQ2F4Y5OvfWymjcwDLw@mail.gmail.com> In-Reply-To: <CAKsGTHR9AzX2v%2B%2BDbNCdt7RwxEfw8jKwndXzH9oxQEHvPszo%2Bw@mail.gmail.com> References: <CAKsGTHR9AzX2v%2B%2BDbNCdt7RwxEfw8jKwndXzH9oxQEHvPszo%2Bw@mail.gmail.com>
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No. It's not from mtx_lock. It's likely from lock contention. Since the list ate the attachment, I can't check for sure, but high CPU usage in locking primitives is a classic sign of poor lock design leading to contention. Warner On Wed, Jun 27, 2018 at 6:28 AM, Steevan Rodrigues <steevanxperia@gmail.com> wrote: > Hi > > I come from Linux background and new to FreeBSD. > > I am investigating a high CPU usage issue on FreeBSD for PCIe driver of a > card . The card can process data at a rate of 30 to 50 Gbps . However, I > see very high CPU usage even when I run a single threaded user side > application which uses this card . > > I ran hotkernel script from Dtrace toolkit. A portion of the output is > given in the attached file dtraceDiff.txt. Here I see that lock_delay > seems to be the reason for high CPU usage. Looks like it comes from mutex > locks > > This driver uses mutex locks ( mtx_lock). > > The CPU usage is very high on a multicore (Xeon CPU) server node than a > dual core (Intel i3) Desktop . > > It shows 30 to 40 % CPU usage on a Intel i3 ( 2 core 4 threads) and 60 to > 70% CPU usage on a Xeon CPU with 12 core (24 threads) for same output > data rate . > > I wonder whether usage of mtx_lock is the cause of high CPU usage ? Any > pointers or suggestions welcome. > > Using FreeBSD 11.1 Release > > Thanks > > Steev > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" > >
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