Re: [PATCH 20/23] fsmonitor: force update index when fsmonitor token advances

From: Derrick Stolee <stolee@gmail.com>
Date: Apr 27, 2021, 14:52 UTC
Message-ID: <91ee1b83-7db6-1578-9725-b3ae263ea023@gmail.com>
In-Reply-To: <d699ad597d2c40cd2c0fe8abbf75b5386d4cf0f2.1617291666.git.gitgitgadget@gmail.com>

On 4/1/2021 11:41 AM, Jeff Hostetler via GitGitGadget wrote:...

Show 10 quoted lines

> +	/*
> +	 * If the fsmonitor response and the subsequent scan of the disk
> +	 * did not cause the in-memory index to be marked dirty, then force
> +	 * it so that we advance the fsmonitor token in our extension, so
> +	 * that future requests don't keep re-requesting the same range.
> +	 */
> +	if (istate->fsmonitor_last_update &&
> +	    strcmp(istate->fsmonitor_last_update, last_update_token.buf))
> +		istate->cache_changed |= FSMONITOR_CHANGED;
> +

This could lead to extra index writes that don't normally happen in the case without the FS Monitor feature. I'm particularly sensitive to this because of my sparse-index work is trying to solve for the I/O cost of large indexes, but perhaps this cost is worth the benefit.

I'll keep an eye out as I do performance testing.

Thanks, -Stolee