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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