Hi, Mika, On 7/23/20 12:05 PM, Alexander Sverdlin wrote: > > Hello Tudor, > > On 22/07/2020 19:03, [email protected] wrote: >> On 7/22/20 7:37 PM, Alexander Sverdlin wrote: > > [...] > >>> I've performed my testing as well and got the following results: >>> >>> Vanilla Linux 4.9 (i.e. before the introduction of the offending >>> patch): >>> >>> dd if=/dev/flash/by-name/XXX of=/dev/null bs=4k >>> 1280+0 records in >>> 1280+0 records out >>> 5242880 bytes (5.2 MB, 5.0 MiB) copied, 3.91981 s, 1.3 MB/s >>> >>> Vanilla 4.19 (i.e. with offending patch): >>> >>> dd if=/dev/flash/by-name/XXX of=/dev/null bs=4k >>> 1280+0 records in >>> 1280+0 records out >>> 5242880 bytes (5.2 MB, 5.0 MiB) copied, 6.70891 s, 781 kB/s >>> >>> 4.19 + revert: >>> >>> dd if=/dev/flash/by-name/XXX of=/dev/null bs=4k >>> 1280+0 records in >>> 1280+0 records out >>> 5242880 bytes (5.2 MB, 5.0 MiB) copied, 3.90503 s, 1.3 MB/s >>>
[cut] > with 10us it looks like this: > > dd if=/dev/flash/by-name/... of=/dev/null bs=4k > 1280+0 records in > 1280+0 records out > 5242880 bytes (5.2 MB, 5.0 MiB) copied, 4.33816 s, 1.2 MB/s > > Which means, there is a performance regression and it would depend on > the test case, how bad it will be... > We need a bit of a context here. Using a tight-loop for polling and having a 5 secs timeout is fishy. For anything that's expected to complete less than a few usec, it's usually better to poll continuously, but then a timeout of 5s is way too big. Can we shrink the timeout to few msecs? I'll queue this to spi-nor/next to fix the perf regression, but I would like to continue the discussion and to come up with an incremental patch on top of this one. Cheers, ta
