Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCHv2 2/5] vmscan: Kill hibernation specific reclaim logic and unify it | Date | Mon, 2 Nov 2009 20:03:52 +0100 |
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On Monday 02 November 2009, KOSAKI Motohiro wrote: > > > Then, This patch changed shrink_all_memory() to only the wrapper function of > > > do_try_to_free_pages(). it bring good reviewability and debuggability, and solve > > > above problems. > > > > > > side note: Reclaim logic unificication makes two good side effect. > > > - Fix recursive reclaim bug on shrink_all_memory(). > > > it did forgot to use PF_MEMALLOC. it mean the system be able to stuck into deadlock. > > > - Now, shrink_all_memory() got lockdep awareness. it bring good debuggability. > > > > As I said previously, I don't really see a reason to keep shrink_all_memory(). > > > > Do you think that removing it will result in performance degradation? > > Hmm... > Probably, I misunderstood your mention. I thought you suggested to kill > all hibernation specific reclaim code. I did. It's no performance degression. > (At least, I didn't observe) > > But, if you hope to kill shrink_all_memory() function itsef, the short answer is, > it's impossible. > > Current VM reclaim code need some preparetion to caller, and there are existing in > both alloc_pages_slowpath() and try_to_free_pages(). We can't omit its preparation.
Well, my grepping for 'shrink_all_memory' throughout the entire kernel source code seems to indicate that hibernate_preallocate_memory() is the only current user of it. I may be wrong, but I doubt it, unless some new users have been added since 2.6.31.
In case I'm not wrong, it should be safe to drop it from hibernate_preallocate_memory(), because it's there for performance reasons only. Now, since hibernate_preallocate_memory() appears to be the only user of it, it should be safe to drop it entirely.
> Please see following shrink_all_memory() code. it's pretty small. it only have > few vmscan preparation. I don't think it is hard to maintainance.
No, it's not, but I'm really not sure it's worth keeping.
Thanks, Rafael
> ===================================================== > unsigned long shrink_all_memory(unsigned long nr_to_reclaim) > { > struct reclaim_state reclaim_state; > struct scan_control sc = { > .gfp_mask = GFP_HIGHUSER_MOVABLE, > .may_swap = 1, > .may_unmap = 1, > .may_writepage = 1, > .nr_to_reclaim = nr_to_reclaim, > .hibernation_mode = 1, > .swappiness = vm_swappiness, > .order = 0, > .isolate_pages = isolate_pages_global, > }; > struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); > struct task_struct *p = current; > unsigned long nr_reclaimed; > > p->flags |= PF_MEMALLOC; > lockdep_set_current_reclaim_state(sc.gfp_mask); > reclaim_state.reclaimed_slab = 0; > p->reclaim_state = &reclaim_state; > > nr_reclaimed = do_try_to_free_pages(zonelist, &sc); > > p->reclaim_state = NULL; > lockdep_clear_current_reclaim_state(); > p->flags &= ~PF_MEMALLOC; > > return nr_reclaimed; > }
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