Re: vm-33, strongly recommended [Re: [2.4.17/18pre] VM and swap - it's really unusable]

Ken Brownfield (ken@irridia.com)
Thu, 11 Apr 2002 18:34:43 -0500


This sounds great, but I still have concerns with using -aa, or subsets
of same.

How much of the improved behavior that you're seeing is due to the vm-33
tweaks and not pte-highmem, block-highmem, or any of the 100 or so other
2.4.19-pre6aa1 patches?

For production use, I prefer to divert from mainline only with my
specific needs (or trivial fixes). Using -aa would introduce a large
array of (to me) unknowns. How many of the -aa patches are "ready" for
mainline and production? vm is currently being debated on the floor --
but what about pte-highmem and block-highmem? How many of the other
patches are as widely tested as the vm patch? For some reason, applying
a patch called "00_readahead-got-broken-somewhere-1" doesn't give me the
utmost confidence in production. Call it a failed bag check.

While 2.4.x is a stable kernel, it needs to be a working* kernel until
2.5 can sort out these and the vast array of other issues. IMHO.
*Admittedly, "working" in this case only applies to larger servers, but
it would be quite tragic to delay the spread of Linux to hardware that's
been available and used in production for _years_. Maybe 5% of the
installed base has relevant hardware, but the benefit to Linux _far_
outstrips that seemingly anemic number. I've probably rehashed that
point too much as it is, but...

What I'd like to hear (and what I suspect many admins trying to get
higher-end hardware working optimally in a production environment would
like to hear) is what specific patches applied to mainline are needed to
correct the current VM and I/O issues in the 2.4 tree?

If it's vm, pte-highmem, and block-highmem, that's fine -- and separable
from -aa. Otherwise it's difficult to get people to test, use, and
provide feedback that isn't polluted by unnecessary variables.

Thanks,

-- 
Ken.
ken@irridia.com

On Wed, Apr 10, 2002 at 01:36:09AM +0200, Andrea Arcangeli wrote: | I recommend everybody to never use a 2.4 kernel without first applying | this vm patch: | | ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/patches/v2.4/2.4.19pre5/vm-33.gz | | It applies cleanly to both 2.4.19pre5 and 2.4.19pre6. Andrew splitted it | into orthogonal pieces for easy merging from Marcelo's side (modulo | -rest that is important too but that it's still quite monolithic, but | it's pointless to invest further effort at this time until we are | certain Marcelo will do its job and eventually merge it in mainline): | | ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/patches/v2.4/2.4.19pre5/ | | So far a first part of those patches is been merged into mainline into | pre5 (not any previous kernel, if you've some problem reproducible with | pre4 pre3 pre2 and pre1 or any previous kernel that's not related to the | async flushing changes, I seen a bogus report floating around to Marcelo | about pre1 pointing to the vm changes, it can't be the vm changes if | it's pre[1234]). | | This VM is under heavy stressing for weeks on my SMP highmem machine | with a real life DBMS workload in a real life setup with huge VM | pressure with mem=1024m and 1.2G of shm pushed in swap constantly by the | kernel, performance of the workload is now very good and exactly | reproducible and constant, so I recommend it for all production systems | (both lowmem desktops and highend servers). | | Alternatively you can use the whole -aa patchkit, to get all the other | critical highend features like pte-highmem, highio etc... | | I haven't bugreports pending on the vm patch. | | Thanks, | | Andrea - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/