linux-kernel - Re: [PATCH 10/25] Calculate the alloc

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Date:	Tue, 21 Apr 2009 19:12:57 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com,
	Linux Memory Management List <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 10/25] Calculate the alloc_flags for allocation only once

> > > +	/* Avoid recursion of direct reclaim */
> > > +	if (p->flags & PF_MEMALLOC)
> > > +		goto nopage;
> > > +
> > 
> > Again. old code doesn't only check PF_MEMALLOC, but also check TIF_MEMDIE.
> > 
> 
> But a direct reclaim will have PF_MEMALLOC set and doesn't care about
> the value of TIF_MEMDIE with respect to recursion.
> 
> There is still a check made for TIF_MEMDIE for setting ALLOC_NO_WATERMARKS
> in gfp_to_alloc_flags() so that flag is still being taken care of.

Do you mean this is intentional change?
I only said there is changelog-less behavior change.

old code is here.
PF_MEMALLOC and TIF_MEMDIE makes goto nopage. it avoid reclaim.
-------------------------------------------------------------------------
rebalance:
        if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
                        && !in_interrupt()) {
                if (!(gfp_mask & __GFP_NOMEMALLOC)) {
nofail_alloc:
                        /* go through the zonelist yet again, ignoring mins */
                        page = get_page_from_freelist(gfp_mask, nodemask, order,
                                zonelist, high_zoneidx, ALLOC_NO_WATERMARKS);
                        if (page)
                                goto got_pg;
                        if (gfp_mask & __GFP_NOFAIL) {
                                congestion_wait(WRITE, HZ/50);
                                goto nofail_alloc;
                        }
                }
                goto nopage;
        }
-------------------------------------------------------------------------


but I don't oppose this change if it is your intentional.




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