On Mon 23-04-18 10:06:08, Mikulas Patocka wrote: > > > On Sat, 21 Apr 2018, Matthew Wilcox wrote: > > > On Fri, Apr 20, 2018 at 05:21:26PM -0400, Mikulas Patocka wrote: > > > On Fri, 20 Apr 2018, Matthew Wilcox wrote: > > > > On Fri, Apr 20, 2018 at 04:54:53PM -0400, Mikulas Patocka wrote: > > > > > On Fri, 20 Apr 2018, Michal Hocko wrote: > > > > > > No way. This is just wrong! First of all, you will explode most likely > > > > > > on many allocations of small sizes. Second, CONFIG_DEBUG_VM tends to be > > > > > > enabled quite often. > > > > > > > > > > You're an evil person who doesn't want to fix bugs. > > > > > > > > Steady on. There's no need for that. Michal isn't evil. Please > > > > apologise. > > > > > > I see this attitude from Michal again and again. > > > > Fine; then *say that*. I also see Michal saying "No" a lot. Sometimes > > I agree with him, sometimes I don't. I think he genuinely wants the best > > code in the kernel, and saying "No" is part of it. > > > > > He didn't want to fix vmalloc(GFP_NOIO) > > > > I don't remember that conversation, so I don't know whether I agree with > > his reasoning or not. But we are supposed to be moving away from GFP_NOIO > > towards marking regions with memalloc_noio_save() / restore. If you do > > that, you won't need vmalloc(GFP_NOIO). > > He said the same thing a year ago. And there was small progress. 6 out of > 27 __vmalloc calls were converted to memalloc_noio_save in a year - 5 in > infiniband and 1 in btrfs. (the whole discussion is here > http://lkml.iu.edu/hypermail/linux/kernel/1706.3/04681.html ) Well this is not that easy. It requires a cooperation from maintainers. I can only do as much. I've posted patches in the past and actively bringing up this topic at LSFMM last two years... > He refuses 15-line patch to fix GFP_NOIO bug because he believes that in 4 > years, the kernel will be refactored and GFP_NOIO will be eliminated. Why > does he have veto over this part of the code? I'd much rather argue with > people who have constructive comments about fixing bugs than with him. I didn't NACK the patch AFAIR. I've said it is not a good idea longterm. I would be much more willing to change my mind if you would back your patch by a real bug report. Hacks are acceptable when we have a real issue in hands. But if we want to fix potential issue then better make it properly. [...] > I sent the CONFIG_DEBUG_SG patch before (I wonder why he didn't repond to > it). I'll send a third version of the patch that actually randomly chooses > between kmalloc and vmalloc, because some abuses can only be detected with > kmalloc and we should test both. > > For bisecting, it is better to always fallback to vmalloc, but for general > testing, it is better to test both branches. Agreed! -- Michal Hocko SUSE Labs
