* Will Newton <will.newton@xxxxxxxxx> [170621 01:18]: > On Wed, Jun 21, 2017 at 7:24 AM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: > > Hi Tony, > > > * Will Newton <will.newton@xxxxxxxxx> [170620 05:39]: > >> Just adding a few people to CC. I'd love to get some feedback as to > >> whether this patch makes sense or not. > >> > >> On Mon, Jun 19, 2017 at 10:36 AM, Will Newton <will.newton@xxxxxxxxx> wrote: > >> > Reduce max_segs to a value that allows allocation of an entire > >> > descriptor list within a single page. This avoids doing a > >> > higher order GFP_ATOMIC allocation when setting up a transfer > >> > which can potentially fail and lead to I/O failures. > > > > I recall we only ever have few SG entries so if there is no performance > > impact I see no reason to lower it to save memory. Care to check > > if that's the case still? > > I have been seeing allocation failures in edma_prep_slave_sg > allocating the descriptor list of order 3, which from my rough > calculations is an sg_len of ~800. The memory usage itself doesn't > seem like a problem but doing a GFP_ATOMIC allocation of higher order > under I/O load seems like it is always going to cause problems. OK > I'm not an expert on this code but it looks like the scatterlist is > created from the queue so if the queue gets full we can get a very > large scatterlist. The current value of 1024 seems to be something of > an outlier: > > drivers/mmc/host/android-goldfish.c: mmc->max_segs = 32; > drivers/mmc/host/atmel-mci.c: mmc->max_segs = 256; > drivers/mmc/host/atmel-mci.c: mmc->max_segs = 64; > drivers/mmc/host/au1xmmc.c: mmc->max_segs = AU1XMMC_DESCRIPTOR_COUNT; > drivers/mmc/host/bcm2835.c: mmc->max_segs = 128; > drivers/mmc/host/bfin_sdh.c: mmc->max_segs = 1; > drivers/mmc/host/bfin_sdh.c: mmc->max_segs = PAGE_SIZE / > sizeof(struct dma_desc_array); > drivers/mmc/host/cavium.c: mmc->max_segs = 16; > drivers/mmc/host/cavium.c: mmc->max_segs = 1; > drivers/mmc/host/dw_mmc.c: mmc->max_segs = host->ring_size; > drivers/mmc/host/dw_mmc.c: mmc->max_segs = 64; > drivers/mmc/host/dw_mmc.c: mmc->max_segs = 64; > drivers/mmc/host/jz4740_mmc.c: mmc->max_segs = 128; > drivers/mmc/host/meson-gx-mmc.c: mmc->max_segs = > SD_EMMC_DESC_BUF_LEN / sizeof(struct sd_emmc_desc); > drivers/mmc/host/mmc_spi.c: mmc->max_segs = MMC_SPI_BLOCKSATONCE; > drivers/mmc/host/mmci.c: mmc->max_segs = NR_SG; > drivers/mmc/host/mtk-sd.c: mmc->max_segs = MAX_BD_NUM; > drivers/mmc/host/mvsdio.c: mmc->max_segs = 1; > drivers/mmc/host/mxcmmc.c: mmc->max_segs = 64; > drivers/mmc/host/mxs-mmc.c: mmc->max_segs = 52; > drivers/mmc/host/omap.c: mmc->max_segs = 32; > drivers/mmc/host/omap_hsmmc.c: mmc->max_segs = 1024; > drivers/mmc/host/pxamci.c: mmc->max_segs = NR_SG; > drivers/mmc/host/rtsx_pci_sdmmc.c: mmc->max_segs = 256; > drivers/mmc/host/rtsx_usb_sdmmc.c: mmc->max_segs = 256; > drivers/mmc/host/sdhci.c: mmc->max_segs = SDHCI_MAX_SEGS; > drivers/mmc/host/sdhci.c: mmc->max_segs = 1; > drivers/mmc/host/sdhci.c: mmc->max_segs = SDHCI_MAX_SEGS; > drivers/mmc/host/sh_mmcif.c: mmc->max_segs = 32; > drivers/mmc/host/tifm_sd.c: mmc->max_segs = mmc->max_blk_count; > drivers/mmc/host/tmio_mmc_pio.c: mmc->max_segs = 32; > drivers/mmc/host/usdhi6rol0.c: mmc->max_segs = 32; > drivers/mmc/host/ushc.c: mmc->max_segs = 1; > drivers/mmc/host/via-sdmmc.c: mmc->max_segs = 1; > drivers/mmc/host/vub300.c: mmc->max_segs = 128; > drivers/mmc/host/wbsd.c: mmc->max_segs = 128; > drivers/mmc/host/wmt-sdmmc.c: mmc->max_segs = wmt_caps->max_segs; OK maybe update the patch description a bit more with that info above :) Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
