On Thu, May 2, 2019 at 5:45 PM Atin Mukherjee <atin.mukherjee83@xxxxxxxxx> wrote:
On Thu, 2 May 2019 at 20:38, Xavi Hernandez <xhernandez@xxxxxxxxxx> wrote:On Thu, May 2, 2019 at 4:06 PM Atin Mukherjee <atin.mukherjee83@xxxxxxxxx> wrote:On Thu, 2 May 2019 at 19:14, Xavi Hernandez <xhernandez@xxxxxxxxxx> wrote:On Thu, 2 May 2019, 15:37 Milind Changire, <mchangir@xxxxxxxxxx> wrote:On Thu, May 2, 2019 at 6:44 PM Xavi Hernandez <xhernandez@xxxxxxxxxx> wrote:Hi Ashish,On Thu, May 2, 2019 at 2:17 PM Ashish Pandey <aspandey@xxxxxxxxxx> wrote:Xavi,I would like to keep this option (features.lock-notify-contention) enabled by default.However, I can see that there is one more option which will impact the working of this option which is "notify-contention-delay"Just a nit. I wish the option was called "notify-contention-interval"The "delay" part doesn't really emphasize where the delay would be put in.It makes sense. Maybe we can also rename it or add a second name (alias). If there are no objections, I will send a patch with the change.Xavi.description = "This value determines the minimum amount of time "
"(in seconds) between upcall contention notifications "
"on the same inode. If multiple lock requests are "
"received during this period, only one upcall will "
"be sent."},I am not sure what should be the best value for this option if we want to keep features.lock-notify-contention ON by default?It looks like if we keep the value of notify-contention-delay more, say 5 sec, it will wait for this much time to send up callnotification which does not look good.No, the first notification is sent immediately. What this option does is to define the minimum interval between notifications. This interval is per lock. This is done to avoid storms of notifications if many requests come referencing the same lock.Is my understanding correct?What will be impact of this value and what should be the default value of this option?I think the current default value of 5 seconds seems good enough. If there are many bricks, each brick could send a notification per lock. 1000 bricks would mean a client would receive 1000 notifications every 5 seconds. It doesn't seem too much, but in those cases 10, and considering we could have other locks, maybe a higher value could be better.Xavi---AshishFrom: "Xavi Hernandez" <xhernandez@xxxxxxxxxx>
To: "gluster-devel" <gluster-devel@xxxxxxxxxxx>
Cc: "Pranith Kumar Karampuri" <pkarampu@xxxxxxxxxx>, "Ashish Pandey" <aspandey@xxxxxxxxxx>, "Amar Tumballi" <atumball@xxxxxxxxxx>
Sent: Thursday, May 2, 2019 4:15:38 PM
Subject: Should we enable contention notification by default ?Hi all,there's a feature in the locks xlator that sends a notification to current owner of a lock when another client tries to acquire the same lock. This way the current owner is made aware of the contention and can release the lock as soon as possible to allow the other client to proceed.This is specially useful when eager-locking is used and multiple clients access the same files and directories. Currently both replicated and dispersed volumes use eager-locking and can use contention notification to force an early release of the lock.Eager-locking reduces the number of network requests required for each operation, improving performance, but could add delays to other clients while it keeps the inode or entry locked. With the contention notification feature we avoid this delay, so we get the best performance with minimal issues in multiclient environments.Currently the contention notification feature is controlled by the 'features.lock-notify-contention' option and it's disabled by default. Should we enable it by default ?I don't see any reason to keep it disabled by default. Does anyone foresee any problem ?Is it a server only option? Otherwise it will break backward compatibility if we rename the key, If alias can get this fixed, that’s a better choice but I’m not sure if it solves all the problems.It's a server side option. I though that an alias didn't have any other implication than accept two names for the same option. Is there anything else I need to consider ?If it’s a server side option then there’s no challenge in alias. If you do rename then in heterogeneous server versions volume set wouldn’t work though.
I created a patch to change this and set notify-contention to 'yes' by default. I'll test upgrade paths to make sure that nothing breaks.
Xavi
----______________________________________________________________________________________________Regards,Xavi
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--Milind
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