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Date: Sat, 12 Feb 2022 00:35:08 -0800 From: Abhinav Kumar <quic_abhinavk@...cinc.com> To: Johannes Berg <johannes@...solutions.net>, Greg KH <gregkh@...uxfoundation.org> CC: <linux-kernel@...r.kernel.org>, <rafael@...nel.org>, <robdclark@...il.com>, <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>, <freedreno@...ts.freedesktop.org>, <seanpaul@...omium.org>, <swboyd@...omium.org>, <nganji@...eaurora.org>, <aravindh@...eaurora.org>, <khsieh@...eaurora.org>, <daniel@...ll.ch>, <dmitry.baryshkov@...aro.org> Subject: Re: [PATCH] devcoredump: increase the device delete timeout to 10 mins Hi Johannes On 2/12/2022 12:24 AM, Johannes Berg wrote: > On Fri, 2022-02-11 at 23:52 -0800, Abhinav Kumar wrote: >> >> The thread is writing the data to a file in local storage. From our >> profiling, the read is the one taking the time not the write. >> > > That seems kind of hard to believe, let's say it's a 4/3 split (4 > minutes reading, 3 minutes writing, to make read > write as you say), > and 3MiB size, that'd mean you get 12.8KiB/sec? That seems implausibly > low, unless you're reading with really tiny buffers? > > Can you strace this somehow? (with timestamp info) > Yes, like I have already mentioned in earlier comments, we continue to check whats taking that long. Once we find something from our analysis and also have the trace, will update the thread. >> Just doubling what we have currently. I am not sure how the current 5 >> mins timeout came from. >> > > To be honest it came out of thin air, and wasn't really meant as a limit > on how fast you can read (feels like even if it's tens of MiB you should > read it in milliseconds into userspace), but more of a maximum time that > we're willing to waste kernel memory if nobody is around to read the > data. > > I thought it'd be better if we could somehow pin it while the userspace > is reading it, but OTOH maybe that's actually bad, since that means > userspace (though suitably privileged) could pin this kernel memory > indefinitely. > > johannes
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