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. 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; > > >> > Signed-off-by: Will Newton <willn@xxxxxxxx> >> > --- >> > drivers/mmc/host/omap_hsmmc.c | 6 +++--- >> > 1 file changed, 3 insertions(+), 3 deletions(-) >> > >> > diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c >> > index 1438a72..d5f42d9 100644 >> > --- a/drivers/mmc/host/omap_hsmmc.c >> > +++ b/drivers/mmc/host/omap_hsmmc.c >> > @@ -2864,9 +2864,9 @@ static int omap_hsmmc_probe(struct platform_device *pdev) >> > host->use_adma = true; >> > } >> > >> > - /* Since we do only SG emulation, we can have as many segs >> > - * as we want. */ >> > - mmc->max_segs = 1024; >> > + /* Set this to a value that allows allocating an entire descriptor >> > + list within a page (zero order allocation). */ >> > + mmc->max_segs = 64; >> > >> > mmc->max_blk_size = 512; /* Block Length at max can be 1024 */ >> > mmc->max_blk_count = 0xFFFF; /* No. of Blocks is 16 bits */ >> > -- >> > 2.7.4 >> > >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-omap" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
