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From: | Richard Henderson |
Subject: | Re: [Qemu-devel] [PATCH 09/22] exec-all: shrink tb->invalid to uint8_t |
Date: | Sun, 9 Jul 2017 10:11:21 -1000 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 07/08/2017 09:50 PM, Emilio G. Cota wrote:
To avoid wasting a byte. I don't have any use in mind for this byte, but I think it's good to leave this byte explicitly free for future use. See this discussion for how the u16 came to be: https://lists.gnu.org/archive/html/qemu-devel/2016-07/msg04564.html We could use a bool but in some systems that would take > 1 byte. Signed-off-by: Emilio G. Cota<address@hidden> --- include/exec/exec-all.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
What I would prefer to do is generalize tb->cflags. Those values *do* affect how we compile the TB, and yet we don't take them into account. So I think it would be a good idea to feed that into the TB hash.
At present we use 18 bits of the uint32_t. That leaves plenty of room for:* the compile-time value of parallel_cpus, so we don't have to keep flushing the TBs that we create for cpu_exec_step_atomic.
* invalid, which no TB within the hashtable would have set. * other stuff which may become relevant in the future. r~
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