| Message ID | 1546145375-793-1-git-send-email-yang.shi@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4,1/2] mm: swap: check if swap backing device is congested or not | expand |
On Sun, Dec 30, 2018 at 12:49:34PM +0800, Yang Shi wrote: > The test on my virtual machine with congested HDD shows long tail > latency is reduced significantly. > > Without the patch > page_fault1_thr-1490 [023] 129.311706: funcgraph_entry: #57377.796 us | do_swap_page(); > page_fault1_thr-1490 [023] 129.369103: funcgraph_entry: 5.642us | do_swap_page(); > page_fault1_thr-1490 [023] 129.369119: funcgraph_entry: #1289.592 us | do_swap_page(); > page_fault1_thr-1490 [023] 129.370411: funcgraph_entry: 4.957us | do_swap_page(); > page_fault1_thr-1490 [023] 129.370419: funcgraph_entry: 1.940us | do_swap_page(); > page_fault1_thr-1490 [023] 129.378847: funcgraph_entry: #1411.385 us | do_swap_page(); > page_fault1_thr-1490 [023] 129.380262: funcgraph_entry: 3.916us | do_swap_page(); > page_fault1_thr-1490 [023] 129.380275: funcgraph_entry: #4287.751 us | do_swap_page(); > > With the patch > runtest.py-1417 [020] 301.925911: funcgraph_entry: #9870.146 us | do_swap_page(); > runtest.py-1417 [020] 301.935785: funcgraph_entry: 9.802us | do_swap_page(); > runtest.py-1417 [020] 301.935799: funcgraph_entry: 3.551us | do_swap_page(); > runtest.py-1417 [020] 301.935806: funcgraph_entry: 2.142us | do_swap_page(); > runtest.py-1417 [020] 301.935853: funcgraph_entry: 6.938us | do_swap_page(); > runtest.py-1417 [020] 301.935864: funcgraph_entry: 3.765us | do_swap_page(); > runtest.py-1417 [020] 301.935871: funcgraph_entry: 3.600us | do_swap_page(); > runtest.py-1417 [020] 301.935878: funcgraph_entry: 7.202us | do_swap_page(); Hi Yang, I guess runtest.py just calls page_fault1_thr? Being explicit about this may improve the changelog for those unfamiliar with will-it-scale. May also be useful to name will-it-scale and how it was run (#thr, runtime, system cpus/memory/swap) for more context.
On 1/2/19 3:00 PM, Daniel Jordan wrote: > On Sun, Dec 30, 2018 at 12:49:34PM +0800, Yang Shi wrote: >> The test on my virtual machine with congested HDD shows long tail >> latency is reduced significantly. >> >> Without the patch >> page_fault1_thr-1490 [023] 129.311706: funcgraph_entry: #57377.796 us | do_swap_page(); >> page_fault1_thr-1490 [023] 129.369103: funcgraph_entry: 5.642us | do_swap_page(); >> page_fault1_thr-1490 [023] 129.369119: funcgraph_entry: #1289.592 us | do_swap_page(); >> page_fault1_thr-1490 [023] 129.370411: funcgraph_entry: 4.957us | do_swap_page(); >> page_fault1_thr-1490 [023] 129.370419: funcgraph_entry: 1.940us | do_swap_page(); >> page_fault1_thr-1490 [023] 129.378847: funcgraph_entry: #1411.385 us | do_swap_page(); >> page_fault1_thr-1490 [023] 129.380262: funcgraph_entry: 3.916us | do_swap_page(); >> page_fault1_thr-1490 [023] 129.380275: funcgraph_entry: #4287.751 us | do_swap_page(); >> >> With the patch >> runtest.py-1417 [020] 301.925911: funcgraph_entry: #9870.146 us | do_swap_page(); >> runtest.py-1417 [020] 301.935785: funcgraph_entry: 9.802us | do_swap_page(); >> runtest.py-1417 [020] 301.935799: funcgraph_entry: 3.551us | do_swap_page(); >> runtest.py-1417 [020] 301.935806: funcgraph_entry: 2.142us | do_swap_page(); >> runtest.py-1417 [020] 301.935853: funcgraph_entry: 6.938us | do_swap_page(); >> runtest.py-1417 [020] 301.935864: funcgraph_entry: 3.765us | do_swap_page(); >> runtest.py-1417 [020] 301.935871: funcgraph_entry: 3.600us | do_swap_page(); >> runtest.py-1417 [020] 301.935878: funcgraph_entry: 7.202us | do_swap_page(); > Hi Yang, I guess runtest.py just calls page_fault1_thr? Being explicit about Yes, runtest.py is the wrapper script of will-it-scale. > this may improve the changelog for those unfamiliar with will-it-scale. Sure. > > May also be useful to name will-it-scale and how it was run (#thr, runtime, > system cpus/memory/swap) for more context. How about the below description: The test with page_fault1 of will-it-scale (sometimes tracing may just show runtest.py that is the wrapper script of page_fault1), which basically launches NR_CPU threads to generate 128MB anonymous pages for each thread, on my virtual machine with congested HDD shows long tail latency is reduced significantly. Without the patch page_fault1_thr-1490 [023] 129.311706: funcgraph_entry: #57377.796 us | do_swap_page(); page_fault1_thr-1490 [023] 129.369103: funcgraph_entry: 5.642us | do_swap_page(); page_fault1_thr-1490 [023] 129.369119: funcgraph_entry: #1289.592 us | do_swap_page(); page_fault1_thr-1490 [023] 129.370411: funcgraph_entry: 4.957us | do_swap_page(); page_fault1_thr-1490 [023] 129.370419: funcgraph_entry: 1.940us | do_swap_page(); page_fault1_thr-1490 [023] 129.378847: funcgraph_entry: #1411.385 us | do_swap_page(); page_fault1_thr-1490 [023] 129.380262: funcgraph_entry: 3.916us | do_swap_page(); page_fault1_thr-1490 [023] 129.380275: funcgraph_entry: #4287.751 us | do_swap_page(); With the patch runtest.py-1417 [020] 301.925911: funcgraph_entry: #9870.146 us | do_swap_page(); runtest.py-1417 [020] 301.935785: funcgraph_entry: 9.802us | do_swap_page(); runtest.py-1417 [020] 301.935799: funcgraph_entry: 3.551us | do_swap_page(); runtest.py-1417 [020] 301.935806: funcgraph_entry: 2.142us | do_swap_page(); runtest.py-1417 [020] 301.935853: funcgraph_entry: 6.938us | do_swap_page(); runtest.py-1417 [020] 301.935864: funcgraph_entry: 3.765us | do_swap_page(); runtest.py-1417 [020] 301.935871: funcgraph_entry: 3.600us | do_swap_page(); runtest.py-1417 [020] 301.935878: funcgraph_entry: 7.202us | do_swap_page(); Thanks, Yang
On Thu, Jan 03, 2019 at 09:10:13AM -0800, Yang Shi wrote: > How about the below description: > > The test with page_fault1 of will-it-scale (sometimes tracing may just show > runtest.py that is the wrapper script of page_fault1), which basically > launches NR_CPU threads to generate 128MB anonymous pages for each thread, > on my virtual machine with congested HDD shows long tail latency is reduced > significantly. > > Without the patch > page_fault1_thr-1490 [023] 129.311706: funcgraph_entry: #57377.796 us | > do_swap_page(); > page_fault1_thr-1490 [023] 129.369103: funcgraph_entry: 5.642us | > do_swap_page(); > page_fault1_thr-1490 [023] 129.369119: funcgraph_entry: #1289.592 us | > do_swap_page(); > page_fault1_thr-1490 [023] 129.370411: funcgraph_entry: 4.957us | > do_swap_page(); > page_fault1_thr-1490 [023] 129.370419: funcgraph_entry: 1.940us | > do_swap_page(); > page_fault1_thr-1490 [023] 129.378847: funcgraph_entry: #1411.385 us | > do_swap_page(); > page_fault1_thr-1490 [023] 129.380262: funcgraph_entry: 3.916us | > do_swap_page(); > page_fault1_thr-1490 [023] 129.380275: funcgraph_entry: #4287.751 us | > do_swap_page(); > > With the patch > runtest.py-1417 [020] 301.925911: funcgraph_entry: #9870.146 us | > do_swap_page(); > runtest.py-1417 [020] 301.935785: funcgraph_entry: 9.802us | > do_swap_page(); > runtest.py-1417 [020] 301.935799: funcgraph_entry: 3.551us | > do_swap_page(); > runtest.py-1417 [020] 301.935806: funcgraph_entry: 2.142us | > do_swap_page(); > runtest.py-1417 [020] 301.935853: funcgraph_entry: 6.938us | > do_swap_page(); > runtest.py-1417 [020] 301.935864: funcgraph_entry: 3.765us | > do_swap_page(); > runtest.py-1417 [020] 301.935871: funcgraph_entry: 3.600us | > do_swap_page(); > runtest.py-1417 [020] 301.935878: funcgraph_entry: 7.202us | > do_swap_page(); That's better, thanks!
diff --git a/mm/swap_state.c b/mm/swap_state.c index fd2f21e..78d500e 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -538,11 +538,18 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, bool do_poll = true, page_allocated; struct vm_area_struct *vma = vmf->vma; unsigned long addr = vmf->address; + struct inode *inode = NULL; mask = swapin_nr_pages(offset) - 1; if (!mask) goto skip; + if (si->flags & (SWP_BLKDEV | SWP_FS)) { + inode = si->swap_file->f_mapping->host; + if (inode_read_congested(inode)) + goto skip; + } + do_poll = false; /* Read a page_cluster sized and aligned cluster around offset. */ start_offset = offset & ~mask;
Swap readahead would read in a few pages regardless if the underlying device is busy or not. It may incur long waiting time if the device is congested, and it may also exacerbate the congestion. Use inode_read_congested() to check if the underlying device is busy or not like what file page readahead does. Get inode from swap_info_struct. Although we can add inode information in swap_address_space (address_space->host), it may lead some unexpected side effect, i.e. it may break mapping_cap_account_dirty(). Using inode from swap_info_struct seems simple and good enough. Just does the check in vma_cluster_readahead() since swap_vma_readahead() is just used for non-rotational device which much less likely has congestion than traditional HDD. Although swap slots may be consecutive on swap partition, it still may be fragmented on swap file. This check would help to reduce excessive stall for such case. The test on my virtual machine with congested HDD shows long tail latency is reduced significantly. Without the patch page_fault1_thr-1490 [023] 129.311706: funcgraph_entry: #57377.796 us | do_swap_page(); page_fault1_thr-1490 [023] 129.369103: funcgraph_entry: 5.642us | do_swap_page(); page_fault1_thr-1490 [023] 129.369119: funcgraph_entry: #1289.592 us | do_swap_page(); page_fault1_thr-1490 [023] 129.370411: funcgraph_entry: 4.957us | do_swap_page(); page_fault1_thr-1490 [023] 129.370419: funcgraph_entry: 1.940us | do_swap_page(); page_fault1_thr-1490 [023] 129.378847: funcgraph_entry: #1411.385 us | do_swap_page(); page_fault1_thr-1490 [023] 129.380262: funcgraph_entry: 3.916us | do_swap_page(); page_fault1_thr-1490 [023] 129.380275: funcgraph_entry: #4287.751 us | do_swap_page(); With the patch runtest.py-1417 [020] 301.925911: funcgraph_entry: #9870.146 us | do_swap_page(); runtest.py-1417 [020] 301.935785: funcgraph_entry: 9.802us | do_swap_page(); runtest.py-1417 [020] 301.935799: funcgraph_entry: 3.551us | do_swap_page(); runtest.py-1417 [020] 301.935806: funcgraph_entry: 2.142us | do_swap_page(); runtest.py-1417 [020] 301.935853: funcgraph_entry: 6.938us | do_swap_page(); runtest.py-1417 [020] 301.935864: funcgraph_entry: 3.765us | do_swap_page(); runtest.py-1417 [020] 301.935871: funcgraph_entry: 3.600us | do_swap_page(); runtest.py-1417 [020] 301.935878: funcgraph_entry: 7.202us | do_swap_page(); Acked-by: Tim Chen <tim.c.chen@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com> --- v4: Added observed effects in the commit log per Andrew v3: Move inode deference under swap device type check per Tim Chen v2: Check the swap device type per Tim Chen mm/swap_state.c | 7 +++++++ 1 file changed, 7 insertions(+)