Chuck Lever wrote: > On Jan 26, 2012, at 9:42 AM, Srinivas KANDAGATLA wrote: > > >> From: Srinivas Kandagatla <srinivas.kandagatla@xxxxxx> >> >> This patch attempts to minimize the delay in nfs root mount, which >> happens as side effect of nfs-root mount retry by changing the >> NFSROOT_TIMEOUT_MIN and NFSROOT_TIMEOUT_MAX values. >> >> Current strategy is, if do_mount_root fails, sleep for 5 seconds for the >> second attempt followed by a 5<<1 seconds delay for each loop with a >> maximum of 30 seconds delay. >> For 5 retries it would take. >> >> 5 + 10 + 20 + 30 + 30 = 95 Seconds >> with >> each do_mount_root timeout @ 3-4 seconds x 5 = 15 seconds. >> >> Which means Kernel can only attempt the succession root-mounts or panic >> after 110 seconds. >> >> So changing min and max timeouts will have the below delays. >> 0 + 1 + 3 + 7 + 15 = 26 Seconds. >> and with >> each do_mount_root timeout @ 3-4 seconds x 5 = 15 seconds. >> Which means Kernel can only attempt the succession root-mounts or panic >> after 41 seconds >> >> As, do_mount_root timesout in 3-4 seconds which should be sufficient >> delay to start of the second nfs mount attempt and increasing delay >> after that makes more sense. >> >> I clearly see an advantange in changing these values because, Without >> this patch my board mounts nfs in 9-10 seconds, however with this patch >> can mount nfs in 4-5 seconds. >> > > This feels like tuning the default settings for a very specific set up. In the original thread for this work, 41 seconds would probably not be long enough for the network switch to enable the port. > Probably you might be right. We could address that by increasing NFSROOT_RETRY_MAX to 7 from 5. However, I want to highlight an another major issue of having an min timeout start at 5. Most of the boards (or SOC's) have in-build ethernet MAC's and external Ethernet PHY's, Linux PHY (& phy state-machine) framework takes on an average of 2-3 seconds from phy_start to get the ethernet PHY into a Link-up state. All those above boards which used to mount NFS in 3-4 seconds prior to the original "NFS: Retry mounting NFSROOT" patch and few other patches, NOW mounts NFS root in 9-10 seconds. Which is the case with all the ST boards and most of the embedded boards with external PHY's fall in. Having the timeout start from 0 will address the uses case mentioned above and increasing the loops from 5 to 8 will increase the total NFS root timeout to 109 seconds. 0 + 1 + 3 + 7 + 15 + 31 + 31 = 88 + each do_mount_root timeout @ 3-4 seconds x 7 = 21 = 109 seconds Finally the intention of the patch was to address most of the use-cases and not just the one I hit, increasing the retries to 7 should address the orignal network switch case and reducing the timeout-min should help other boards do nfs mounts as quickly as it used to happen before. Let me know if this sounds OK to you so that I can generate a new patch? Thanks, srini > I don't have a better solution at this time, but I think the current defaults will work (possibly with added delay) on most systems, whereas the proposed settings will probably result in more panics. I prefer to keep the current settings until we have a solution that doesn't break other systems. > > >> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxx> >> --- >> Hello All, >> With latest kernel I can see that my nfs-root mounts with big delay >> of 5 seconds when compared to 2.6.32. It took 9-10 seconds, where as in 2.6.32 it took 4-5 seconds. >> >> However with modifications to NFSROOT_TIMEOUT_MIN and NFSROOT_TIMEOUT_MAX, nfs root mounts as it used to do it in 2.6.32. >> As first nfs mount timeout itself introduces sufficient delay to start the second retry. >> I think changing the min-max values will help people to nfs boot there boards faster than it is in 3.3 kernel. >> >> Comments ? >> >> Thanks. >> srini >> >> >> >> init/do_mounts.c | 6 +++--- >> 1 files changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/init/do_mounts.c b/init/do_mounts.c >> index ef6478f..b8214ce 100644 >> --- a/init/do_mounts.c >> +++ b/init/do_mounts.c >> @@ -361,8 +361,8 @@ out: >> >> #ifdef CONFIG_ROOT_NFS >> >> -#define NFSROOT_TIMEOUT_MIN 5 >> -#define NFSROOT_TIMEOUT_MAX 30 >> +#define NFSROOT_TIMEOUT_MIN 1 >> +#define NFSROOT_TIMEOUT_MAX 32 >> #define NFSROOT_RETRY_MAX 5 >> >> static int __init mount_nfs_root(void) >> @@ -390,7 +390,7 @@ static int __init mount_nfs_root(void) >> break; >> >> /* Wait, in case the server refused us immediately */ >> - ssleep(timeout); >> + ssleep(timeout - 1); >> timeout <<= 1; >> if (timeout > NFSROOT_TIMEOUT_MAX) >> timeout = NFSROOT_TIMEOUT_MAX; >> -- >> 1.6.3.3 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" 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-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
