netdev - RE: [PATCH net 1/3] rhashtable: don't test for shrink on insert, expansion on delete

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Date:	Fri, 20 Feb 2015 10:08:26 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Daniel Borkmann' <daniel@...earbox.net>,
	"davem@...emloft.net" <davem@...emloft.net>
CC:	"tgraf@...g.ch" <tgraf@...g.ch>,
	"johunt@...mai.com" <johunt@...mai.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ying Xue <ying.xue@...driver.com>
Subject: RE: [PATCH net 1/3] rhashtable: don't test for shrink on insert,
 expansion on delete

From: Daniel Borkmann
> Restore pre 54c5b7d311c8 behaviour and only probe for expansions on inserts
> and shrinks on deletes. Currently, it will happen that on initial inserts
> into a sparse hash table, we may i.e. shrink it first simply because it's
> not fully populated yet, only to later realize that we need to grow again.
> 
> This however is counter intuitive, e.g. an initial default size of 64
> elements is already small enough, and in case an elements size hint is given
> to the hash table by a user, we should avoid unnecessary expansion steps,
> so a shrink is clearly unintended here.

Does it actually make sense to shrink below the initial default size?

	David

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