Date: Fri, 4 Nov 2016 19:05:55 +0100 From: Ben RUBSON <ben.rubson@gmail.com> To: freebsd-fs <freebsd-fs@FreeBSD.org> Subject: Re: ZFS L2ARC checksum errors after compression Message-ID: <6D16D1E0-CA33-44DB-AB88-9257A8BDE67F@gmail.com> In-Reply-To: <3bd7cb79-ec5a-3b7c-0642-24a7b1f001e6@FreeBSD.org> References: <921575537.20161029143626@serebryakov.spb.ru> <3dae7691-fcd1-b3b9-445c-b81d6f0cdc52@FreeBSD.org> <fe4962d6-75c3-32c0-8d28-c99661e5161f@FreeBSD.org> <3bd7cb79-ec5a-3b7c-0642-24a7b1f001e6@FreeBSD.org>
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> On 04 Nov 2016, at 15:20, Andriy Gapon <avg@FreeBSD.org> wrote:
>=20
> On 03/11/2016 21:43, Lev Serebryakov wrote:
>> On 29.10.2016 16:32, Andriy Gapon wrote:
>>=20
>> Looks like L2ARC is unusable now if your have compression enabled on
>> FSes. It shows 2x compression (ALLOC =3D 2xSIZE), and tons of =
checksum
>> errors. I simply don't have compressible enough data on my FSes! It =
is
>> mostly media files! Looks like this data is bogus.
>>=20
>>> I think that a recent upstream change, compressed ARC support, =
reintroduced an a
>>> old problem that was fixed a while ago.
>>=20
>=20
> Lev,
>=20
> because of the confusing variable names I made a mistake in the patch =
that I
> offered you. Could you please try a new slight different patch?
> (...)
> + if ((write_psize + asize) > target_sz) {
Do you think the issue comes from this test ?
target_sz is only the threshold under which we still have to write =
buffers to L2.
Note that I also proposed a modification around this test in the =
following PR :
https://github.com/openzfs/openzfs/pull/189
Here is an extract of the interesting code :
uint64_t size =3D arc_hdr_size(hdr);
passed_sz +=3D size;
if (passed_sz > headroom) {
/*
* Searched too far.
*/
mutex_exit(hash_lock);
break;
}
if (!l2arc_write_eligible(guid, hdr)) {
mutex_exit(hash_lock);
continue;
}
if ((write_asize + size) > target_sz) {
full =3D B_TRUE;
mutex_exit(hash_lock);
break;
}
Note that I also faced the 16.0E bug in 11.0-RC3 (which has not =
compressed ARC support) :
https://www.illumos.org/issues/7410
Ben
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