| Message ID | 20240405013547.1859126-5-yosryahmed@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | zswap same-filled and limit checking cleanups | expand |
On Fri, Apr 05, 2024 at 01:35:46AM +0000, Yosry Ahmed wrote: > These knobs offer more fine-grained control to userspace than needed and > directly expose/influence kernel implementation; remove them. > > For disabling same_filled handling, there is no logical reason to refuse > storing same-filled pages more efficiently and opt for compression. > Scanning pages for patterns may be an argument, but the page contents > will be read into the CPU cache anyway during compression. Also, > removing the same_filled handling code does not move the needle > significantly in terms of performance anyway [1]. > > For disabling non_same_filled handling, it was added when the compressed > pages in zswap were not being properly charged to memcgs, as workloads > could escape the accounting with compression [2]. This is no longer the > case after commit f4840ccfca25 ("zswap: memcg accounting"), and using > zswap without compression does not make much sense. > > [1]https://lore.kernel.org/lkml/CAJD7tkaySFP2hBQw4pnZHJJwe3bMdjJ1t9VC2VJd=khn1_TXvA@mail.gmail.com/ > [2]https://lore.kernel.org/lkml/19d5cdee-2868-41bd-83d5-6da75d72e940@maciej.szmigiero.name/ > > Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
diff --git a/mm/zswap.c b/mm/zswap.c index b92fa37bee277..a85c9235d19d3 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -123,19 +123,6 @@ static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */ module_param_named(accept_threshold_percent, zswap_accept_thr_percent, uint, 0644); -/* - * Enable/disable handling same-value filled pages (enabled by default). - * If disabled every page is considered non-same-value filled. - */ -static bool zswap_same_filled_pages_enabled = true; -module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled, - bool, 0644); - -/* Enable/disable handling non-same-value filled pages (enabled by default) */ -static bool zswap_non_same_filled_pages_enabled = true; -module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled, - bool, 0644); - /* Number of zpools in zswap_pool (empirically determined for scalability) */ #define ZSWAP_NR_ZPOOLS 32 @@ -1368,9 +1355,6 @@ static bool zswap_is_folio_same_filled(struct folio *folio, unsigned long *value unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1; bool ret = false; - if (!zswap_same_filled_pages_enabled) - return false; - page = kmap_local_folio(folio, 0); val = page[0]; @@ -1460,9 +1444,6 @@ bool zswap_store(struct folio *folio) goto store_entry; } - if (!zswap_non_same_filled_pages_enabled) - goto freepage; - /* if entry is successfully added, it keeps the reference */ entry->pool = zswap_pool_current_get(); if (!entry->pool)
These knobs offer more fine-grained control to userspace than needed and directly expose/influence kernel implementation; remove them. For disabling same_filled handling, there is no logical reason to refuse storing same-filled pages more efficiently and opt for compression. Scanning pages for patterns may be an argument, but the page contents will be read into the CPU cache anyway during compression. Also, removing the same_filled handling code does not move the needle significantly in terms of performance anyway [1]. For disabling non_same_filled handling, it was added when the compressed pages in zswap were not being properly charged to memcgs, as workloads could escape the accounting with compression [2]. This is no longer the case after commit f4840ccfca25 ("zswap: memcg accounting"), and using zswap without compression does not make much sense. [1]https://lore.kernel.org/lkml/CAJD7tkaySFP2hBQw4pnZHJJwe3bMdjJ1t9VC2VJd=khn1_TXvA@mail.gmail.com/ [2]https://lore.kernel.org/lkml/19d5cdee-2868-41bd-83d5-6da75d72e940@maciej.szmigiero.name/ Signed-off-by: Yosry Ahmed <yosryahmed@google.com> --- mm/zswap.c | 19 ------------------- 1 file changed, 19 deletions(-)