stop logd or
setprop ctl.stop logd makes
logcat completely unavailable (which may break some apps/daemons) and isn't persistent across reboots. For permanently removing
logd you need to delete
/system/etc/init/logd.rc file which defines this
init service. But it's not recommended.
/data/misc/logd/ directory is filled by
logcatd which is a sub-service of main
256 MB is the default size but can be changed if required (1).
logd mainly covers the functionality of its desktop counterpart syslogd, but also includes klogd and partially auditd to get logs from SELinux subsystem of kernel. However
logd just reads from (RAM) memory buffers and doesn't save to persistent memory (files) by default. Reason is evident, these saved logs are of no use to a majority of users (as you), but too many write requests for these logs reduce flash memory (eMMC) life unnecessarily.
If one needs these logs as files, a separate service named
logcat daemon which itself reads from
logd) can save them to filesystem (on
eng builds only since Oreo (2)). Going through the resources (3, 4), it's easy to control this service permanently (persistent across reboots) by setting property
clear) or by using shell scripts