Re: Very slow scp performance comparing to Linux
- In reply to: Wei Hu : "RE: Very slow scp performance comparing to Linux"
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Date: Tue, 29 Aug 2023 08:28:57 UTC
On 8/29/23, Wei Hu <weh@microsoft.com> wrote: > > >> -----Original Message----- >> From: Guido Falsi <mad@madpilot.net> >> Sent: Monday, August 28, 2023 6:49 PM >> To: Wei Hu <weh@microsoft.com>; Mikhail Zakharov >> <zmey20000@yahoo.com>; freebsd-hackers@freebsd.org >> Subject: Re: Very slow scp performance comparing to Linux >> >> On 28/08/23 12:03, Wei Hu wrote: >> > Hi Mike, >> > >> > All VMs are with same type and they are in Azure. If the copy on Linux >> > is >> being cached on the RX side, so is FreeBSD? >> > >> >> You could perform the test using files in memory filesystems (tmpfs or >> the >> like). This would factor out disk performance whatever the backend. >> > Thanks, Guido. I tried tmpfs on the RX side with both FreeBSD and Linux VMs. > > The throughput on FreeBSD went up significantly from 50 MB/s to 630 MB/s > with > NIC interface. Linux went up modestly form 550 MB/s to 660 MB/s. > > So, looks in the non-tmpfs case, the Linux ext4 filesystem does cache large > amounts > of data in memory, much larger than FreeBSD ufs. > > Many thanks, Mike for bringing this up and Guido, for the suggestion to try > tmpfs. > There is probably something funky going on here. Here is a hack which will collect basic profiling info, works in a vm: dtrace -w -n 'profile:::profile-4999 { @[sym(arg0)] = count(); } tick-10s { system("clear"); trunc(@, 40); printa("%40a %@16d\n", @); clear(@); }' so start scp, start dtrace and see what happens -- Mateusz Guzik <mjguzik gmail.com>