[PATCH 5/5] mm improvements

Nick Piggin
2004-02-04T09:42:44Z

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Nick Piggin wrote:

> 5/5: vm-tune-throttle.patch
> Try to allocate a bit harder before giving up / throttling on
> writeout.
>

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This patch causes try_to_free_pages to wakeup_bdflush even if it has
reclaimed the required # of pages on the first scan.

It allows two scans at the two lowest priorities before breaking out or
doing a blk_congestion_wait, for both try_to_free_pages and balance_pgdat.

linux-2.6-npiggin/mm/vmscan.c | 38 +++++++++++++++++++++-----------------
1 files changed, 21 insertions(+), 17 deletions(-)

diff -puN mm/vmscan.c~vm-tune-throttle mm/vmscan.c
--- linux-2.6/mm/vmscan.c~vm-tune-throttle 2004-02-04 14:09:46.000000000 +1100
+++ linux-2.6-npiggin/mm/vmscan.c 2004-02-04 14:09:46.000000000 +1100
@@ -930,22 +930,33 @@ int try_to_free_pages(struct zone **zone

if (nr_reclaimed >= nr_pages) {
ret = 1;
+ if (gfp_mask & __GFP_FS)
+ wakeup_bdflush(total_scanned);
goto out;
}
+
+ /* Don't stall on the first run - it might be bad luck */
+ if (likely(priority == DEF_PRIORITY))
+ continue;
+
+ /* Let the caller handle it */
if (!(gfp_mask & __GFP_FS))
- break; /* Let the caller handle it */
+ goto out;
+
/*
- * Try to write back as many pages as we just scanned. Not
- * sure if that makes sense, but it's an attempt to avoid
- * creating IO storms unnecessarily
+ * Try to write back as many pages as we just scanned.
+ * Not sure if that makes sense, but it's an attempt
+ * to avoid creating IO storms unnecessarily
*/
wakeup_bdflush(total_scanned);

/* Take a nap, wait for some writeback to complete */
blk_congestion_wait(WRITE, HZ/10);
}
- if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY))
+
+ if (!(gfp_mask & __GFP_NORETRY))
out_of_memory();
+
out:
for (i = 0; zones[i] != 0; i++)
zones[i]->prev_priority = zones[i]->temp_priority;
@@ -1004,6 +1015,7 @@ static int balance_pgdat(pg_data_t *pgda
if (to_reclaim <= 0)
continue;
}
+ all_zones_ok = 0;
zone->temp_priority = priority;
reclaimed = shrink_zone(zone, GFP_KERNEL,
to_reclaim, &nr_scanned, ps, priority);
@@ -1017,16 +1029,6 @@ static int balance_pgdat(pg_data_t *pgda
continue;
if (zone->pages_scanned > zone->present_pages * 2)
zone->all_unreclaimable = 1;
- /*
- * If this scan failed to reclaim `to_reclaim' or more
- * pages, we're getting into trouble. Need to scan
- * some more, and throttle kswapd. Note that this zone
- * may now have sufficient free pages due to freeing
- * activity by some other process. That's OK - we'll
- * pick that info up on the next pass through the loop.
- */
- if (reclaimed < to_reclaim)
- all_zones_ok = 0;
}
if (nr_pages && to_free > 0)
continue; /* swsusp: need to do more work */
@@ -1034,9 +1036,11 @@ static int balance_pgdat(pg_data_t *pgda
break; /* kswapd: all done */
/*
* OK, kswapd is getting into trouble. Take a nap, then take
- * another pass across the zones.
+ * another pass across the zones. Don't stall on the first
+ * pass.
*/
- blk_congestion_wait(WRITE, HZ/10);
+ if (priority < DEF_PRIORITY)
+ blk_congestion_wait(WRITE, HZ/10);
}

for (i = 0; i < pgdat->nr_zones; i++) {

_